《黄帝内经·灵枢·平人绝谷》
小肠周长二寸半，直径八又三分之一分，长三丈二尺，可以容纳谷物二斗四升，水六升三又三分之二合。
小肠大二寸半，径八分分之少半，长三丈二尺，受榖二斗四升，水六升三合合之大半，
The small intestine has a circumference of two and a half inches, a diameter of eight and one third inches, and a length of three zhang and two feet; it can hold two dou and four sheng of grains and six sheng and three and two third he of water.