Lonnies concept of the value of life and sin are rather abramaic (Judeastic/Christrian/Islamic) in religions that believe in re-incarnation that view doesn't always make much sense as I'm sure you'll realise
I don't know if this is what you were thinking of but in Japan there are a number of mummies:
http://www.jref.com/culture/japanese_buddhist_ mummies.shtml
These are mummified Budhist monks who fasted to extreme levels ate only certain plants ( a lot of pine needles as I recall) and put their bodies through extreme physical exercise.
Finally they went off to a cave and drank a lot of water from the arsnic rich stream there, if they were sucessfull they died in the snow there and became mummies - if not they rotted.
I think the practice was banned by the Japanese Government years ago though.