Heavy pumice stone

...The name given to stones used by young people to test their strength, to contests of strength, and to the act of lifting them. They are called banmoishi, omokaruishi, banbuchi, hakariishi, and in Okinawa, sashiishi. The stones are round or oval in shape, and weigh anywhere from 60-70kg to nearly 200kg. Some are engraved with the name of the person who lifted them or their weight.

*Some of the terminology that refers to "pumice" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…若者たちの力試し，力競べ用の石，およびその行為に対する呼称。番持石，重軽（おもかる）石，バンブチ，ハカリ石，沖縄ではサシ石などという。石の形は丸型か楕円型で，重さは60～70kgから200kg近く，持ち上げた人の名や重量を刻んだものもある。…

※「重軽石」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報