《黄帝内经·灵枢·卫气行》
漏壶水下二十五刻，卫气行于手足太阳经，这是半个白昼中卫气运行的度数。
水下二十五刻，人气在太阳，此半日之度也。
When water in the clepsydra drops 25 minutes, Wei Qi runs in the hand-foot sun meridian, which is the degree of Wei Qi movement in half a day.