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Self-Mummification for Dummies
The process of becoming a self-made mummy is long, slow and excruciatingly painful, taking from three to ten years. The procedure the monks followed developed over a 900 year period, and though there were different variations, it generally consisted of three equal states, each 1000 days long. For the first 1000 day period the monk adopted a strict diet that consisted of only small amounts of soba (buckwheat) dough and walnuts, hazelnuts, and nutmeg gathered from the surrounding forest. The diet served to reduce the ascetic's body fat dramatically, and as fat decomposes quickly after death, it increased the chances of successful mummification. In the second 1000 day period, the ascetic's diet became even more limited: only bark and the roots of pine tree were ingested. The monk became increasingly emaciated as his body fat reduced to nothingness and his body's water-content similarly declined. Though greatly weakened and increasingly skeletal in appearance, the monk continued to subject himself to long periods of prayer and chanting mantras.
Nearing the end of the second 1000 day period, the monk drank tea made from the juice of the Urushi, or Japanese Varnish tree. A caustic, extremely toxic sap—even its vapour can cause a rash—it is usually used to make a highly durable coating for Chinese and Japanese lacquerware. Drinking the tea caused the monk to vomit, perspire and urinate extensively, further reducing the fluids in his body, as well as causing a large build up of poisons. These poisons, however, played an important part of the mummification process, for they would also kill any organism that tried to consume the priest's flesh after death.
The monk, by then severely debilitated and, one assumes, in tremendous physical pain, was ready for the third and final stage in the process, described in a pamphlet from Kaikoji Temple: “When the priests were near death, stone shelters were constructed three metres underground. The priests were then put into wooden coffins and buried in the shelters with only a bamboo tube for air. In the coffins the priests continued their ascetic practices, sitting in meditation, reciting mantras, and maintaining their strict diet.”
Entombed in his subterranean chamber with only bark and roots to eat and a bell to signal their continued existence to the other monks, the initiate waited for death. “When the sounds of their prayers [or the bell] could no longer be heard, the priests were dug up to confirm their deaths and were then reburied. After three years and three months, they were again dug up, placed in shrines, and worshipped as living gods.” Unlike other mummies, the process finished with death: “No other methods were used in the mummification process”—hence the presence of internal organs that scholars were amazed to discover.
Having successfully attained Buddahood, the mummies were usually taken to a particular temple, where generations of monks such as Ato-san tended for them. In the hilltop Kaikoji Temple in Sakata, Yamagata Prefecture, we found two very well preserved sokushinbutsu, Chukai and Enmyokai, who are enshrined side by side in their quiet suburban temple. The two gods today sit in the same position in which they were lowered into the ground to die, in 1755 and 1822 respectively, and face the three holy mountains of Dewa Sanzan where they undertook their rites.
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source: http://cjmathews.com/sokushinbutsu.html