The Emperor Ming Huang of the T’ang dynasty, also known as T’ang Hsüan Tsung, in the reign-period K’ai Yüan (A.D. 712–742), after an expedition to Mount Li in Shensi, was attacked by fever. During a nightmare he saw a small demon fantastically dressed in red trousers, with a shoe on one foot but none on the other, and a shoe hanging from his girdle. Having broken through a bamboo gate, he took possession of an embroidered box and a jade flute, and then began to make a tour of the palace, sporting and gambolling. The Emperor grew angry and questioned him. “Your humble servant,” replied the little demon, “is named Hsü Hao, ‘Emptiness and Devastation,’” “I have never heard of such a person,” said the Emperor. The demon rejoined, “Hsü means to desire Emptiness, because in Emptiness one can fly just as one wishes; Hao, ‘Devastation,’ changes people’s joy to sadness. “The Emperor, irritated by this flippancy, was about to call his guard, when suddenly a great devil appeared, wearing a tattered head-covering and a blue robe, a horn clasp on his belt, and official boots on his feet. He went up to the sprite, tore out one of his eyes, crushed it up, and ate it. The Emperor asked the newcomer who he was. “Your humble servant,” he replied, “is Chung K’uei, Physician of Tung-nan Shan in Shensi. In the reign-period Wu Tê (A.D. 618–627) of the Emperor Kao Tsu of the T’ang dynasty I was ignominiously rejected and unjustly defrauded of a first class in the public examinations. Overwhelmed with shame, I committed suicide on the steps of the imperial palace. The Emperor ordered me to be buried in a green robe [reserved for members of the imperial clan], and out of gratitude for that favour I swore to protect the sovereign in any part of the Empire against the evil machinations of the demon Hsü Hao.” At these words the Emperor awoke and found that the fever had left him. His Majesty called for Wu Tao-tzŭ (one of the most celebrated Chinese artists) to paint the portrait of the person he had seen in his dream. The work was so well done that the Emperor recognized it as the actual demon he had seen in his sleep, and rewarded the artist with a hundred taels of gold. The portrait is said to have been still in the imperial palace during the Sung dynasty.
Another version of the legend says that Chung K’uefs essay was recognized by the examiners as equal to the work of the best authors of antiquity, but that the Emperor rejected him on account of his extremely ugly features, whereupon he committed suicide in his presence, was honoured by the Emperor and accorded a funeral as if he had been the successful first candidate, and canonized with the title of Great Spiritual Chaser of Demons for the Whole Empire.