National Treasures & Important Cultural Properties
of National Institutes for Cultural Heritage, Japan

Most of the ancient inkstones were earthenware, not made of stone. There were two types; those where broken pieces of traditional Japanese sueki pottery cups, pots or jars were used and others that were made as inkstones from the beginning.
These are inkstones produced by working on the shoulder parts of large sueki jars made in the first half of the eighth century. As for N-78, the marks of lacquer reveal that there was a wooden frame and two feet originally. As for N-79, the wooden frame and the entire back side are lacquered and there are no feet. Both are well used and their surfaces are worn down. There is a possibility that they were produced later on. Tradition says that N-79 was owned by Shotoku Taishi, however, the date of the inkstone doesn't correspond to his time.