《左传·隐公·隐公五年》
舞，用来调节八种材料所制乐器的乐音而传播八方之风。所以人数在八行以下。 
夫舞所以节八音而行八风，故自八以下。 
The dance is used to regulate the musical notes of the musical instruments made of eight materials and to spread the winds of the eight directions. Therefore, the number of performers is less than eight.