《黄帝内经·灵枢·卫气行》
一昼夜合计水下一百刻，太阳运行二十八舍，整整一个周天。太阳每运行一星宿，漏壶水下三又七分之四刻。《大要》说： 通常是每当太阳行到下一个星宿开始的时间，卫气也恰好运行到手足太阳经。所以，太阳每运行完一个星宿的时间，卫气刚好循行完太阳经、少阳经、阳明经三个阳经还有阴分，卫气就是这样一直周期运行而不停止。 
大要曰： 常以日之加于宿上也，人气在太阳，是故日行一舍，人气行三阳行与阴分，常如是无已。 
A total of 100 minutes of water is combined day and night, and the sun runs 28 sheds, which is exactly one week. Every time the sun runs a constellation, three and seven-quarters minutes of water drop in the clepsydra. **The main points**: Usually, when the sun reaches the next constellation, Wei Qi will also run to the hand-foot sun meridian. Therefore, every time the sun runs a constellation, Wei Qi just circulates the sun meridian, the shaoyang meridian, the Yangming meridian and the yin part. Wei Qi runs in this cycle without stopping.