The idea of mummifying oneself seems quite specific, especially if they ritualized it and had some cocktail of botanicals they ingested to facilitate the process. Is there a name for this 3rd century Chinese Buddhist monastic culture and practice?
The "body in buddha" x-ray showed an iron band supporting the head. There is an explanation in the above paper.
Sokushinbutsu (即身仏) are a kind of Buddhist mummy. In Japan the term refers to the practice of Buddhist monks observing asceticism to the point of death and entering mummification while alive.
Mendicants, these two extremes should not be cultivated by one who has gone forth. What two? Indulgence in sensual pleasures, which is low, crude, ordinary, ignoble, and pointless. And indulgence in self-mortification, which is painful, ignoble, and pointless. Avoiding these two extremes, the Realized One woke up by understanding the middle way of practice, which gives vision and knowledge, and leads to peace, direct knowledge, awakening, and extinguishment.
I'm reasonably certain you're quite well aware of this. I just wanted to ensure a between the lines meaning was made explicit in the thread. To remind that Buddhism is nested inside a larger contingent, and that this story lies more in that outer part than in.