As Kuo Hsi, a painter of the Sung Dynasty, has pointed out, in painting natural scenes there must be left room for the sky and the earth. The ultimate taboo is to "scribble over the entire scroll," as this seems to be "filling in the eye of the beholder," and leaves people with a sense of unease.
就像宋代畫家郭熙曾經指出：畫山水要在畫幅上留天、地的位置，最忌「塗抹滿幅」，因為這樣看來「填塞人目」，令人不快。