‘The Japanese climate is not exactly conducive to mummification. There are no peat bogs, no arid deserts, and no alpine peaks perennially encased in ice. The summers are hot and humid. Yet somehow a group of Buddhist monks from the Shingon sect discovered a way to mummify themselves through rigorous ascetic training in the shadow of a particularly sacred peak in the mountainous northern prefecture of Yamagata.
Between 1081 and 1903, at least 17 monks managed to mummify themselves. The number may well be higher, however, as it is likely some mummies were never recovered from the alpine tombs.
These monks undertook such a practice in emulation of a ninth-century monk named Kūkai, known posthumously as Kōbō Daishi, who founded the esoteric Shingon school of Buddhism in 806. In the 11th century a hagiography of Kūkai appeared claiming that, upon his death in 835, the monk did not die at all, but crawled into his tomb and entered nyūjō, a state of meditation so profound that it induces suspended animation. According to this hagiography, Kūkai plans to emerge in approximately 5.67 million years to usher a predetermined number of souls into nirvana.’