What are the three wonderful books in ancient times?

The three marvelous ancient books refer to Shan Hai Jing, Yijing and Huangdi Neijing. The Classic of Mountains and Seas is a book describing pictures, and it is a strange book in ancient China. The content is mainly geographical knowledge in folklore, including mountains and rivers, nationalities, products, medicine, sacrifices, witch doctors and so on. , with extraordinary literary value. I ching covers philosophy, politics, life, literature, art, science and many other fields. It is an ancient book that no one can really understand since the Qin and Han Dynasties. Huangdi Neijing is a comprehensive medical work, which lays a foundation for understanding human physiology, pathology, diagnosis and treatment. It is a medical work with great influence in China and is called the medical ancestor.