According to historical records, Lao Tzu went out to Hangu Pass in the west and was ordered to write a book in Yin, leaving behind a 5,000-word magnum opus "Tao Te Ching" in the history of China thought. Then he rode on a big green cow and went west, but there was no news. This has aroused the interest of many archaeologists and historians, but so far no conclusive evidence has been drawn. Some people say that he went to India through quicksand, and I went to India to preach and taught a great disciple like Sakyamuni. Many people in the past dynasties thought that this statement was just made up by Taoism in order to raise itself and belittle other religions. Some people say that Lao Tzu settled in Lintao, Gansu Province in his later years, and taught retired elders to refine inner alchemy, maintain health and cultivate monasticism. After gaining the Tao, he "soared" on Lintao Transcendental Platform. Others guessed at random that the law and order was poor at that time, and someone might rob halfway and cause accidental death.