From the you-still-look-good-grandpa dept.
Sokushinbutsu
refers to a practice of Buddhist monks observing austerity to the point of death and mummification
It means, eating and drinking yourself to death in a way that would 'naturally' mummify your body so it would not rot.
REALLY.
It involves eating pine needles and bark, drinking tea made from the bark of the urushi tree (which contains the same chemical that makes poison ivy so unpleasant), and (to be truly successful) drinking water from a spring with near-fatal levels of arsenic.
For the DIY types,
https://en.wikipedia.org/wiki/Sokushinbutsu [wikipedia.org]
https://www.damninteresting.com/sokushinbutsu-the-ancient-buddhist-mummies-of-japan/ [damninteresting.com]
DISCLAIMER: DON'T DIY!