It is said that the soshobako (complaints box written with different kanji) which was established in front of 一の橋御門 of Wakayama-jo Castle when Yoshimune was the lord of the Kishu domain was the origin of meyasubako.
吉宗が紀州藩主時代に和歌山城一の橋御門前に設置した訴訟箱が目安箱に繋がったと言われる。