yuán dū yǐ wéi jīng 缘督以为经
Following the Du Meridian as the Law
This expression means to follow the natural meridian as a constant rule. This comes from Zhuangzi’s work “On Nurturing Life.” Du (督) refers here to the meridian along the human spine, central yet without form. Zhuangzi (369?-286 BC) held that the laws governing natural phenomena had the same characteristics. He differentiated this from narrow-minded and conventional moral laws. “Following the Du meridian as the law” means following a natural law, which is fair and invisible, and allows man to traverse among all things under heaven without running contrarily to them.
Following the natural meridian as a common law, a person can take good care of his health, his life, and his family members, and enjoy longevity. (Zhuangzi)