The length of Sho, a wind instrument, is one shaku (= 30.3 cm) and seven sun (= 3.03 cm x 7), and it was a large Sho until the beginning of Kamakura period, in the thirteenth century, but it became smaller afterward.
管楽器の笙は1尺7寸、13世紀の鎌倉初期までは大きな笙だったがその後は小さくなった。