Practical Taoism - Thomas Cleary

„Zhang Ziyang said, “The way of restorative alchemy is most simple and easy; it is like a circle.” Yu Yuwu said, “What is the circle? It is the Absolute of the Book of Changes. When the Absolute goes into motion, it produces yin and yang. When motion culminates, it reverts to stillness and in stillness produces yin. When stillness culminates, it returns to movement. Movement and stillness in alternation constitute bases for each other. This is the wonder of Creation, the natural course of the Way.” “