There is a tradition with Buddhist monks that has since been outlawed where they mummify themselves. The remove all fat from their diet and do several other things to prepare this happens over the course of several months in which time they become very thin. They are then sealed in a cave that has air flow with a bell, they ring the bell everyday to show they are still alive. When they have not rung the bell for a couple of days the cave is completely sealed for several months. When the cave is opened, if they have done all the steps correctly, they are mummified. They usually sit in the lotus position while in the cave and are thus mummified in that position. This is all voluntary and they can change their minds at any point during the process. I actually should use the past tense for this as it has been outlawed.