In one, Emperor Xuanzong called him to paint a wall of his palace. He painted a wall mural displaying a rich nature-scene set in a valley, containing a stunning array of flora and fauna and including a cave at the foot of a mountain. The story goes that he informed the emperor that it's not just what the emperor is able to see, Wu Daozi has made this painting in such a way, that a spirit dwells in the cave. Next, he clapped his hands and entered the cave, inviting the emperor to follow. The painter entered the cave but the entrance closed behind him and, before the astonished emperor could move or utter a word, the painting vanished from the wall. This story depicts the spirituality of art. The contemporary Swedish writer Sven Lindqvist meditates on this legend and the challenge that it poses to modern aesthetics in his book, "The Myth of Wu Tao-Tzu."