Hsiang-yen Chih-hsien

Hsiang-yen Chih-hsien 香嚴(or 香巖)智閑 (Hànyǔ Pīnyīn: Xiāngyán Zhìxián; Rōmaji: Kyōgen Chikan, c. 820–898) was a T'ang dynasty Ch'an master of the House of Kuei-yang. A Dharma heir of Kuei-shan Ling-yu 溈山靈祐 (Hànyǔ Pīnyīn: Wéishān Língyòu; Rōmaji: Isan Reiyū, 771–853), the story of Hsiang-yen's enlightenment is rather famous in the Zen tradition. According to his enlightenment story, he had been an accomplished scholar of Buddhist sūtras, but for many years had made very little headway in his meditation practice. One day, his master asked him what his original face was before birth, to which he could not respond—this question became his kōan, and he subsequently burned his sūtras and set out to settle the matter. One day, while working, he heard the sound of a tile striking the ground and attained enlightenment.

Additionally, there is a kōan attributed to Hsiang-yen in The Gateless Gate: the story is that of a man hanging in a tree by his teeth being asked why Bodhidharma came west; how the man is to respond became this famous kōan.