SuttaCentral
As the suttas quoted above says, it’s about those who are higher than stream entrants who are able to attain jhana.
Those below who have developed their spiritual faculties of faith, effort, mindfulness, unification and insight are called dhamma followers (dhammanusarin) and faith-follower (saddhanusarin).
Establishing a meditation practice daily in any posture is far more important than the posture itself. As the meditation practice is a gradual and slow processes spanning this life or many lives we should not rush to attain higher state of mind through certain impossible postures and then start hating the practice itself. If a person sitting in a chair practices diligently, ardently, persistently and continuously will 100% move to the cross legged posture for sure😀
Eh, what has the geometrical arrangement of bones to do with the liberation of citta?
My personal conclusion is: If you’re lucky enough to have the right anatomy for effortless cross-legged / lotus sitting, then go for it - simply because it’s a very stable seat and you’ll not need much cognitive attention to stay in the posture. And if you can sit for hours like that go and see some hardcore korean zen monks, because then the right posture matters in the long run.
If you just sit for 30 minutes or 60 minutes possible negative effects of a not-perfect-posture will not be that grave.
I myself am not blessed with an anatomy conducive for 4-hours-sessions (in spite of 15 years of meditation, no matter what other ‘experienced’ meditators said). So I usually sit on a bench, with the legs tucked underneath. It’s fairly stable and for me it works because there is enough body tension to keep the mind energized.
Usually lying down is not for beginners because it invites the mind to wander off. But if someone is beyond the habitual dozing off, or someone is energized, or sufficiently motivated, and can keep lying in one posture for an hour or two without moving - then anyone give me a non-esoteric or non-dogmatic reason to force oneself into a posture that imitates a Buddha-statue.
Btw, correct me anyone if I’m wrong, but to my knowledge the literal translation of pallaṅkaṃ ābhujitvā is not ‘cross-legged’ but ‘bent around the lap/hip’, or ‘bent into a round lap’ (SuttaCentral)
I am more likely to move to a comfy chair. 
You have to cross the floods not striving too hard or too soft,
Meditative pain or in Dhamma we objectively address it as unpleasant sensations will arise in any posture ,if we sit continuously for a longer period of time, even on top of the queen Elizabeth’s throne.
. These are 70% psychological and 30% physical in nature, It is the manifestation of past avertive sankaras in the from of unpleasant sensations. There is a very thin line dividing craving and meditation, if we continue to change position to avoid pain in any posture that means we are craving for pleasant sensation s.Then there won’t be any difference between meditation and normal day to day life where in we avoid unpleasant situations and crave to be comfortable.In my personal experience Progress in this path heavily depends on how skillfully we use the unpleasant sensations to flush out deep rooted aversions. Our ultimate goal is to achieve equanimity which is the state of mind free from craving and aversions. Normally unpleasant sensations are considered as meditators goldmine.Buddha’s intention was to show us the three marks of existence impermanence, nonself and suffering through meditative pleasure and pain. That is why he calls suffering as a noble truth. We can only reach nibbana out of suffering not out of pleasure.
When we are doing periods of intensive practice, the bi-directional relationship between mental tension and physical tension becomes very clear.
The combination of maintaining postures we’re unaccustomed to for lengthy periods together with over-efforting typically gives rise to tensions that reinforce and build upon each other. Thus by day 3 of the retreat we often get the sore knees, stiff necks etc etc. The usual yogi complaints.
When the mind becomes sufficiently collected and gains in ease however, the body too relaxes in a radical way, and all the physical aches and pains vanish. Thus we can sit perfectly comfortably for many hours without risking the sort of physical injury that we may incur if the muscles were tense, knotted etc.
As @Gabriel mentioned, lying posture is fanstastic for most people as it gives the body a chance to really relax (though take care not to fall asleep). One of my teachers recommends immediately following it up with a sitting period: with a very relaxed body, the mind also tends to relax and we can enjoy some very lovely, collected sitting meditation.
If we can only reach Nibbana out of suffering, then what is jhana for? Or did you mean we can only reach Nibbana out of insight? I’m not a fan of the “no pain, no gain” approach to meditation, partly because this attitude can demotivate people, and partly because there is plenty of dukkha to observe off the cushion. It does depend what you are trying to develop on the cushion of course.
Be careful not to spread any myths. Yes, we can transcend pain, and yes, nice meditations make it easier for the body. But there are no miracles happening, you can transcend pain in meditation and mess up your knees, hips, and back. You are lucky that it doesn’t happen to you, but we shouldn’t give people the wrong idea that meditation will somehow magically make all negative physical consequences of excessive sitting go away.
Nobody should delegate their responsibility for their body to anyone else, their teacher or other ‘experts’. Will anyone else experience your pain? Will your meditation friend or teacher take the bill for the surgery?..
The best is to learn from the responses of the body, without fear. At times we push more, and then we see what happens. At other times we transcend pain in meditation and then sit for a long time - that is fine, just learn from your bodily reactions afterwards if you should improve your posture or should change the posture for these long sittings altogether. Romanticism is out of place when it comes to the body.
Thank you, Gabriel. 
Re-reading my post I see I did not express my thoughts clearly and gave a wrong impression.
I quite agree with everything you said.
I’m sorry if I misrepresented you, I just wanted to counter a possible message of ‘samadhi takes care of everything’. Amazing things do happen, there is just no way to know from the outside if the pain is purely mind-made or has a physiological basis.
Buddha himself tried to reach nibbana through jhana, he mastered all the eight stages of absorption concentration. Then he found out defilement s are deeply rooted in subconscious mind which appear throughout the body as pleasant, unpleasant and neutral sensations with respective roots of greed,ill will and ignorance. Then he invented vipassana (insight) practice to gain experiential wisdom namely impermanence, nonself and suffering to reach nibbana.
As I am not an expert on jhana. We in India householders practice vipassana directly under the Guidance of S.N.Goenka in 10 days retreat. Goenka teaches vipassana immediately after three days of anapana .It is extremely effective if we are able practice at home diligently, ardently, persistently and continuously .
You’re absolutely right that is the reason why majority of the world population gets demotivated without clear understanding of Dhamma. If we are able to reach nibbana comfortably nothing like it
Meditating on a single intense pain has yielded little useful material personally. I can see it vary in intensity and even fade away but this shouldn’t be seen as a ‘miraculous method’ for getting rid of pain. The suffering in pain isn’t done by removing the pain but rather by being detached and not taking it as ‘my pain’ or letting the pain magnify by letting it give rise to defilements and ending rebirth. If you want to get rid of the pain just move your leg and there’s no need for the Noble eightfold path. I find lessening the pain of multiple small pains over the years a better approach and doing so without seeking it out.
Bhikkhus, when the uninstructed worldling is being contacted by a painful feeling, he sorrows, grieves, and laments; he weeps beating his breast and becomes distraught. He feels two feelings—a bodily one and a mental one. Suppose they were to strike a man with a dart, and then they would strike him immediately afterwards with a second dart, so that the man would feel a feeling caused by two darts. So too, when the uninstructed worldling is being contacted by a painful feeling … he feels two feelings—a bodily one and a mental one.
“Being contacted by that same painful feeling, he harbours aversion towards it. When he harbours aversion towards painful feeling, the underlying tendency to aversion towards painful feeling lies behind this. Being contacted by painful feeling, he seeks delight in sensual pleasure. For what reason? Because the uninstructed worldling does not know of any escape from painful feeling other than sensual pleasure. When he seeks delight in sensual pleasure, the underlying tendency to lust for pleasant feeling lies behind this. He does not understand as it really is the origin and the passing away, the gratification, the danger, and the escape in the case of these feelings. When he does not understand these things, the underlying tendency to ignorance in regard to neither-painful-nor-pleasant feeling lies behind this.
“If he feels a pleasant feeling, he feels it attached. If he feels a painful feeling, he feels it attached. If he feels a neither-painful-nor-pleasant feeling, he feels it attached. This, bhikkhus, is called an uninstructed worldling who is attached to birth, aging, and death; who is attached to sorrow, lamentation, pain, displeasure, and despair; who is attached to suffering, I say.
“Bhikkhus, when the instructed noble disciple is contacted by a painful feeling, he does not sorrow, grieve, or lament; he does not weep beating his breast and become distraught. He feels one feeling—a bodily one, not a mental one. Suppose they were to strike a man with a dart, but they would not strike him immediately afterwards with a second dart, so that the man would feel a feeling caused by one dart only. So too, when the instructed noble disciple is contacted by a painful feeling … he feels one feeling—a bodily one, not a mental one.
“Being contacted by that same painful feeling, he harbours no aversion towards it. Since he harbours no aversion towards painful feeling, the underlying tendency to aversion towards painful feeling does not lie behind this. Being contacted by painful feeling, he does not seek delight in sensual pleasure. For what reason? Because the instructed noble disciple knows of an escape from painful feeling other than sensual pleasure. Since he does not seek delight in sensual pleasure, the underlying tendency to lust for pleasant feeling does not lie behind this. He understands as it really is the origin and the passing away, the gratification, the danger, and the escape in the case of these feelings. Since he understands these things, the underlying tendency to ignorance in regard to neither-painful-nor-pleasant feeling does not lie behind this. SuttaCentral
I like the sound of “arm-chair Nibbana”. 
please call me when you reach nibbana on arm chair, because I am breaking my legs in crossed legs to reach there:grinning:
How to build equanimity then?how to eradicate the deep rooted sankaras of anger,hatredness, conciet,anxiety etc …without the help of pain. ?
Sounds like Goenka practice indeed 
How about: with tools which don’t militarize the mind?
Even though early Buddhism was more austere than we usually think and seeing advantages in discomforts, self-inflicted pain is generally discouraged and more seen as a deluded practice of Jains and certain Brahmins. Pain as a phenomenon is unavoidable but the beauty of citta and love are portrayed as much more powerful tools.
Usage of pain, seeing goldmine in pain, releasing aversions through pain are to be realized and not to be intellectualized. When Goenkaji tells these in the midst of intense pain during retreats ,I too had thought and felt like ‘military training’. To practically experience this we need to practice vipassana diligently, ardently, persistently and continuously at home for a longer periods of time. As we pass through some important junctions in the practice we will start understanding the noble qualities of unpleasant sensations (meditative pain).
What are these, junctions?
As we practice vipassana we naturally pass through or otherwise also we have to pass through these two stages for progress
1 Bhanga - dissolution of the body
2. Triggering of defilements - where in mind will start the purification process on its own. Layers of sankaras will start comming out from the subconscious mind. At this time when the mind is exposed to meditative pain, unpleasant or stressful situation, anxieties, anger, hatredness etc an unpleasant sensation arises in the body, if we do not react mentally, verbally and physically layers of past karmic debt or sankaras will start releasing out otherwise they will multiply deep inside and make us suffer that’s what is samsara