It is said that the shape of a hoju represents those of urns for Buddha bones or that a hoju is the beautiful ball-shaped gem that was said to have come out of a dragon god, and that a hoju is placed on a palm of Buddhist statues, for example those of Jizo Bosatsu (Jizo Bodhisattva).
宝珠は釈迦の骨壺（舎利壺）の形とも、龍神の頭の中から出てきたという珠のこととも言われ、地蔵菩薩などの仏像が手のひらに乗せているものである。