One of the key stones mentioned in Tsukiyamateizōden (zenpen) and Tsukiyamateizōden (kōhen). According to the former work, it is placed on the side of an artificial hill. It is also called mikoshi ishi.
Japanese Garden Dictionary: A Glossary for Japanese Gardens and Their History (C) 2010 by Ono Kenkichi and Walter Edwards. All rights reserved.