Laozi
A seventh-century work, the Sandong Zhunang ("Pearly Bag of the Three Caverns"), said Laozi pretended to be a farmer when reaching the western gate, but was recognized by Yinxi, who asked to be taught by the great master. Yinxi wanted to find the Tao and said his long study of astrology allowed him to recognize Laozi. Yinxi was accepted by Laozi as a student. This shows the testing a seeker must undergo before being accepted as a student of a master.