Calligraphic forms must must resemble sitting and walking, flying and moving, going away and approaching, lying down and arising, being sad and happy, insects eating the leaves of trees, sharp swords and long halberds, a mighty bow and rigid arrow, water and fire, clouds and mists, or the sun and moon. It is only when writing presents, this way and that, forms that may be viewed as such images that it can be called calligraphy.

(Cai Yong, 132–192)