Estimates of the number of self-mummified priests in Japan range between sixteen and twenty-four priests. Impressive though this number is, many more have tried to self-mummify themselves; In fact, the practice of self-mummification -- which is a form of suicide, after all -- had to be outlawed towards the end of the 19th century to prevent Buddhist priests from offing themselves this way... and yet the grand majority of priests who have tried to do this have failed. The reasons will take some explaining -- but first, some background on the whole practice and the reasons for it.
So truely devoted Buddhist priests are not afraid of death; but they don't normally seek it either, as this too would be an abnormal obsession with the physical world. The priests that chose to practice self-mummification were usually all older men, who knew they had limited time left to their lives anyway... and since the practice takes years to lead to a sucessful death and mummification, it cannot be characterized as an attempt to reach enlightenment quickly as a normal suicide might be. Rather, the intended purpose of this practice for these priests is to both push their ability to disregard their physical selves to the limit of their ability, and to try and leave an artifact of this struggle that will stand as a symbol of their beliefs to those that are priests after them.
How to be a self-made mummify
Scientific study of the mummies and the process that created them only began in the early 1960's. It was generally expected that the mummies studied would show signs of having been mummified after death by other priests, in much the way Egyptian mummies -- and almost all other mummies on Earth -- have been created. The first step in that process is the removal of the internal organs, because the bacteria in these begin the process of decomposition within hours of death; with these removed, it is relatively easy to prepare, dry, and preserve the remainder of the body. But x-rays discounted this expectation... the internal organs were intact, which meant that mummification had been accomplished in some new way that scientists had not yet encountered. So the process itself was next investigated.
The actual practice was first pioneered by a priest named Kuukai over 1000 years ago at the temple complex of Mount Kooya, in Wakayama prefecture. Kuukai was founder of the Shingon sect of Buddhism, which is the sect that came up with the idea of enlightenment through physical punishment. There were three steps in the process of self-mummification that Kuukai proposed, and the full process took upwards of ten years to lead to a successful mummification.
The first step is a change of diet. The priest was only allowed to eat nuts and seeds that could be found in the forests surrounding his temple; this diet had to be stuck to for a 1000 day period, a little under three years. During this time, the priest was to continue to subject himself to all sorts of physical hardship in his daily training. The results were that the body fat of the priest was reduced to nearly nothing, thus removing a section of the body that easily decomposes after death.
In the second stage, the diet became more restrictive. The priest was now only allowed to eat a small amount of bark and roots from pine trees (mokujiki). This had to be endured for another 1000 day period, by the end of which the priest looked like a living skeleton. This also decreased the overall moisture contained in the body; and the less fluid left in the body, the easier to preserve it.
Towards the end of this 1000 day period, the priest also had to start to drink a special tea made from the sap of the urushi tree. This sap is used to make laquer for bowls and furniture; but it is also very poisonous for most people. Drinking this tea induced vomenting, sweating, and urination, further reducing the fluid content of the priest's body. But even more importantly, the build up of the poison in the priest's body would kill any maggots or insects that tried to eat the priest's remains after death, thus protecting it from yet another source of decay.
The third and 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. But why did some mummify and some not? This is the tricky part of the whole process.
It is not clear if this is part of the process as set down by Kuukai, but in Yamagata is a sacred spring. This spring is on a mountain called Yudono, which is in fact the third sacred mountain of the three I visited in 1998. Many of the priests in the area considered both the water and the mineral deposits from this spring to have medicinal value, and may have injested one or both previous to their entombment. An analysis of the spring water and deposits revealed that they contain enough arsenic to kill a human being! Arsenic does not get eliminated from the body, so it remains after death... and it is toxic to bacteria and other micro-organisms, so it eliminated the bacteria that started the decompostion of the body.
As you can see, the process of self-mummification was a long and extremely painful process that required a mastery of self-control and denial of physical sensation. The self-made mummies of Japan are people who have earned the respect now shown to them, as they exemplify the teachings of the Shingon sect of Japanese Buddhism.