Yellow Emperors Classic of Internal Medicine
Question: “I have heard that in ancient times the people lived to be over a hundred years, and yet they remained active and did not become decrepit in their activities. But nowadays people reach only half of that age and yet become decrepit and failing.”
Answer: In ancient times people understood the “Tao” (the way of being) and patterned themselves after the “Yin and Yang” the two divine principles of creation, masculine and feminine, whose existence is reflected in nature.