Hirao Nyujōzuka Excavated Artifacts and Excavation Survey Materials

Hirao Nyujōzuka

Near the boundary between Hirao in Inagi City and Asao Ward in Kawasaki City, there is a mound called Nyujozuka. Nyujo generally refers to entering meditation or the passing of a saint. Kukai, the founder of Shingon Buddhism, taught that one should wait for the arrival of Maitreya Buddha by entering meditation, and this teaching led to the practice of Nyujo by Shingon monks in various regions after the medieval period. They would chant scriptures while alive and be buried inside the mound, undergoing rigorous training to await the arrival of Maitreya Buddha.
The Nyujozuka in Hirao was excavated in 1959. From the inscription on a stone tablet unearthed, it was revealed that a monk named Nagak信 entered Nyujo on August 15, 1536. The mound is square, measuring approximately 10.8 meters on each side, and inside the mound is a main area measuring about 1.8 meters by 2.1 meters. It is believed that pillars were erected at the four corners of this location to create a room enclosed by boards, where the Nyujo training took place. The top of this main area was covered with a layer of clay, and additional soil was piled on top to form the mound.
A total of 103 items, including one ritual knife believed to have been used for ceremonies, 44 copper coins that were brought from China, and seven iron nails thought to have been used to construct the facilities in the main area, along with 51 items of excavation materials, have been designated as tangible cultural properties of Inagi City.

Hirao Nyujōzuka Excavated Items

The excavated artifacts from the designated burial mound include a total of 52 items: 44 copper coins, 7 iron nails, and 1 iron knife.
The copper coins are foreign coins from China, including Tang coins, Song coins, and Ming coins, some of which have illegible inscriptions. The majority of the coins found are Song coins (from the 10th to the 13th century). These copper coins are believed to have been used in the ritual of entering meditation. During the medieval period, the minting of currency in Japan was not active, and foreign coins from China were predominantly in circulation. It is thought that the foreign coins commonly circulated at that time were used in the ritual of entering meditation.
The iron nails were discovered alongside charred wood around the main body. They range in length from 8 centimeters to 13 centimeters and are significantly deteriorated, but they are square in cross-section and are believed to have been used as nails when constructing the wooden enclosure of the main body. The iron knife measures 24.5 centimeters in length and 2 centimeters in maximum width, and it is thought to have been used for the rituals conducted at the main body.

Excavation Survey Materials

This is the material created from the excavation survey conducted in August 1959. The materials include 2 rubbings of stone tablets, 14 detailed drawings of the site and structures, 33 survey photographs, and 2 draft manuscripts, totaling 51 items. The rubbings are from 2 of the 9 stone tablets unearthed from the main body. One of the rubbings features the inscription "In the fifth year of Tenmon, on the 15th day of the month of Hino, the monk Choshin entered Nirvana," making it a valuable resource that reveals the construction date of the Nirvana mound and the name of the monk who entered Nirvana. The detailed drawings include the overall measurement of the mound, floor plans of the structures, cross-sectional diagrams of the soil layers, and floor plans of unearthed artifacts (such as stone tablets) and iron nails. The survey photographs depict the overall view of the Nirvana mound, cross-sections of the soil layers, the condition of the unearthed stone tablets, the state of the clay layers, the condition of the unearthed coins, the overall view of the main body, and the condition of the floor surface of the main body. The draft manuscripts are believed to be rough drafts for the survey report, detailing the location, scale, facilities of the main body, and the condition of the unearthed stone tablets. In total, there are 15 sheets of 400 characters each. These excavation survey materials, along with the artifacts unearthed from the Nirvana mound, are considered indispensable and important resources for understanding the reality of the medieval Nirvana mounds and the circumstances of the excavation survey.