There is a line in the Therigatha, repeated with variations, which appears in 2.5,
Saṅghāṭiṁ nikkhipitvāna, pattakañca nikujjiya;
which Bihkkhu Sujato renders,
Having laid down my outer robe, and overturned my bowl,
I am unable to understand the meaning of these gestures. They seem here to suggest attainment of an enlightenment beyond what can be attained by rote observance of the vinaya?
Disclaimer: I have no idea if there’s any special meaning to the gestures described, or in the specific words used, but I loved the verse and here’s what arose for me when I read it. Don’t take this as the “scholarly” answer to your question.
The renunciant there specifically says she is sick, feeble and skinny. Any person in that situation would probably be overcome with concern about their life and how to preserve it. The bhikkhuni here, instead, seems to me to take a different approach. She lays down the outer robe that keeps her warm and which she’d have to put on to travel to an inhabited area and maybe ask for help, and she overturns the bowl, which is her only source of sustenance. Rather than relying on these temporary means for survival, she lets go, leans on a rock and abandons even the craving for existence, dispelling the mass of darkness.
Thank you for bringing this to my attention. I think I’ll use it as a teaching tool
with metta and in gassho
The commentary says that the meaning here is quite literal:
saṅghāṭiṃ nikkhipitvānāti santaruttarā eva hutvā yathāsaṃhataṃ aṃse ṭhapitaṃ saṅghāṭiṃ hatthapāse ṭhapetvā.
pattakañca nikujjiyāti mayhaṃ valañjanamattikāpattaṃ adhomukhaṃ katvā ekamante ṭhapetvā.
Wearing the lower and upper robe, having set within arm’s reach the well-folded outer robe,
having turned the clay bowl requisite face down, having placed it to one side, …
Yes, I assume this is just the safest way to place a bowl on the ground if you don’t have a stand. Also harder for critters to poo in if you don’t have a lid.
Turning the bowl upside down is also a Vinaya procedure, but it relates to lay people which doesn’t seem to be the case here.
I’m not sure that these readings are exclusive to each other. 
I’ve observed that in Thag/Thig, it seems there are quite a bit more poetical devices employed compared to Nikayas proper.
One such device is double-entendre descriptions which represent both the inner mind of the poet and the external reality. So I wouldn’t be surprised if that were the case here. (In any case, doesn’t this poetical reading resonate with the aim and method of the Dharma? 
)
I’ll take a look at my notes back home for some other examples later on.
Of course, an example that makes it quite explicit is obviously the famous Thag 1.1, but perhaps this can be understood implicitly in other places as well:
My hut is roofed and pleasant, sheltered from the wind:
so rain, heavens, as you please!
My mind is serene and freed,
I practice wholeheartedly: so rain, heavens!
Oh, after reading Bhante’s response about it being a literal thing, I felt reassured that I wasn’t reading too much into it.
A tiny bit related to the topic…
In the Thai language, the word to overturn the bowl means to boycott. I think it is related to a vinaya rule as mentioned by @Khemarato.bhikkhu.
My thanks to all who have responded! As for me, I think Khemarato.bikkhu’s comment, seconded by Snowbird, most persuasive. The bhikkuni seems to have simply put down her things and rested on a convenient rock and then been vouchsafed enlightenment after a lifetime of striving. I was reading too much into the gestures. It’s a short poem, and it’s unlikely to be overloaded with additional poem’s worth of esoteric meaning. The fact that the next poem, 2.6, has the same phrase, suggests that it’s simply a poetic formula, a rote phrase for preparing to rest. The action of setting down one’s things could be read as metaphoric, but that is, I think, a legitimate interpretation, not a level of meaning which is absolutely structural and necessary to the poem.
