Shaku originated from the breadth between the thumb and forefinger when they are opened, and sun seems to have been invented independently from shaku, but anyway, sun began to be set at the length of a tenth shaku during the age of Zhou Dynasty China.
尺は親指と人差指を広げた時の幅であり、元々の寸は尺とは独立に発生したものと考えられるが、周代に尺の10分の1とされるようになった。