Measurement unit and the ruler used to make the measurements. Many of the rulers in the Shōsō-in were beautifully decorated ritual implements. The standard unit of measuring length in the Nara period was the Tenpyō shaku (29.6 cm), which was based on the Tang dynasty equivalent, the chi (also 29,6 cm). One shaku is made up of ten sun, and one sun comprises ten bu. The kane-shaku (30.3 cm) used today in Japan is longer than its predecessor.