I think I found what I’m looking for in Acaranga Sutra 1.8(7).7.2-8 / 228-53. Here is the text translation by Johannes Bronkhorst in his book The Two Traditions of Meditation in Ancient India:
When a monk thinks: ‘I am indeed tired of carrying around this body in these circumstances’, he should gradually reduce his food; having gradually reduced his food and diminished his passions, his body being prepared, standing like a plank, his body pacified, … he should ask for grass; having asked for grass and received it, he should go away to a lonely place; having gone away to a lonely place … he should spread the grass; and having spread the grass, at that occasion, he should reject body, activity, and movement … (228).
The firm ones, having reached the [ways of] liberation, powerful and wise, knowing all that is excellent, (229)
Having conquered the twofold (birth and death?), the awakened ones have gone to the other shore of the doctrine. And one rids oneself of activity when he has thought [about this] in due order.(230)
(1) Having diminished his passions he bears with little food. In case the monk gets ill in the presence of food, (231)
He should not long for life, nor strive after death; he should not be attached to either, life or death. (232)
Impartial, intent on the destruction of activity (nijjarå) he should preserve his concentration. Renouncing internally as well as externally he strives after a pure heart. (233)
Whatever means he may know to secure his life [for another while, let the wise one quickly avail of that for an intervening period. (234)
Having looked for a place in a village or in the wilderness, and knowing it to be with little life, the monk should spread out the grass. (235)
He should lie without food; when affected [by discomfort] in that [position] he should bear it. He should not go beyond the boundary [which he has set himself], even when he has been affected by things human. (236)
He should not hurt nor rub away living creatures which creep on the ground, or fly high or low, and eat his flesh and blood. (237)
Creatures injure his body, yet he should not walk from his place. Being pained by all kinds of outside influences, he should bear [it all], (238)
going to the other shore of his span of life, [free] from all kinds of knots. This is well-accepted by the self-controlled and understanding person. (239)
(2) The following is another practice taught by the son of Naya (= Mahåv¥ra). One should abandon movement in the threefold three ways, except for [keeping] himself [alive]. (240)
He should not sit down on green plants, but lie on the bare ground after inspecting it; renouncing, taking no food, he should bear [discomfort] when affected [by it] in that [position]. (241)
While feeling aversion to his senses, the monk may take [as much food] as is appropriate. Nevertheless, he is blameless who is motionless and concentrated. (242)
He may step forward and backward, contract and stretch [his limbs], in order to keep body [and soul] together; or, alternatively, he [may become] unconscious in that same position. (243)
He may walk around when tired, or [remain] standing as before. When tired of standing he may finally sit down. (244)
While sitting he directs his senses to the excellent death [which he is going to die]. In case he stumbles upon a termite hill [for support], he should search for something different. (245)
He does not lean on something from which something avoidable could originate. He should pull himself up from there and bear all that affects him. (246)
(3) This one is [even] more intent (ayatatare) [on reaching the goal] who keeps to the following. While controlling all his limbs, let him not move away from his place. (247)
This is the best practice, better than the preceding. Having cleansed [the place] for a short time, the Brahmin should remain there standing. (248)
Having reached a place free from living beings, he should place himself there. He should renounce his body; thinking ‘there are no afflictions in my body, afflictions and troubles [last] as long as life’, he should bear them, being restrained, realizing that they lead to the destruction of the body. (249-50)
He should not be attached to desires for transitory things, even when [they become] more numerous. He should not nourish wishes and greed, since he is looking for the unchanging character. (251)
But this is seemingly that the Jain liberation is ultimately achieved through starving to death, even though Mahavira enlightenment (kevalin jnana) is achieved when he is alive (there is an account of Mahavira asceticism and enlightenment in last part of Acaranga Sutra book 1). Any comment? 