Japanese Buddhist Monks

To prevent decomposition of a body , a mummifier usually removes the organs. Researchers in the 1960s were thus surprised at the fully intact mummies of Japan's Yamagata province—their organs had begun to dry before death. To remove the illusions of the physical world, earn over a million years in heaven, and achieve enlightenment before reincarnation, the most devoted Shingon Buddhist monks mummified themselves as an act of salvation for humanity. 

The monk would eat only fruit and nuts for three years, then pine needles and bark for another three. He would even drink poison tea to keep insects away from his body. Finally, the monk would meditate in a tomb using a breathing tube. He would ring a bell occasionally to signal that he was still alive, and when the bell ringing stopped his acolytes sealed the tomb. After another three years, they opened it. If the monk's body had no decay, he was worshipped as a Living Buddha. Even if he failed, he was buried with special honors. Out of hundreds who tried , only 24 monks ever achieved "Living Buddha" status. 

In 1877, Japan's Emperor Meiji declared this illegal , and today, nobody advocates for it.