It is known that approximately 24 Buddhist monks slowly mummiffied themselves with the purpose of disregarding their physical self. This practice was performed by followers of Shugendo, an ancient form of Buddhism, and the full process took upwards of 10 years.
There were 3 steps in the process of self-mummification:
During 1000 days, the monk could only eat nuts and seeds while taking part in a regimen of rigorous physical activity in order to loose all the body fat.
For another 1000 days, he was only allowed to eat bark and roots. He’d also start drinking a poisonous tea to induce vomiting, sweating and urinating, to eventually reduce the fluid content on the monk’s body. This tea would also prevent any maggots or insects to eat the monk’s remains after death.
The last step of the process was to be entombed alive in a stone room just big enough for a man to sit lotus style in for a final 1000 day period. As long as the priest could ring a bell each day a tube remained in place to supply air; but when the bell finally stopped, the tube was removed and the tomb was sealed.
When the tomb was finally opened, the results would be known. Some few would be fully mummified, and immediately be raised to the rank of Buddha; but most just rotted and, while respected for their incredible endurance, were not considered to be Buddhas. These were simply sealed back into their tombs.