One of oldest examples of ancient calligraphy thought to come directly from the Heavens.

"Cloud formations were associated with the movement of spirits, which were believed to dwell in mist, emerging suddenly to manifest themselves before human beings. A purple flash, or clouds of five colours, frequently marked such supernatural events. But these spiritual contacts too could be controlled by the magic power of calligraphy, and the various cloud-motifs employed in Taoist graphics serve this very purpose. Thus a variety of superbly linear and vapoury 'Cloud Scipt' forms derive their shapes and therefore their magic power from cloud formations. They are believed to have special powers to enable man to communicate with the spirit world, hence their extensive use in talismanic graphic art. Cloud formations, with or without constellations, also provide the model for the magic art of movement, and even geomancy. Sound was believed to penetrate this mysterious cloudy spirit world, so that talismans were often used in combination with spoked charms, incantations, and chants. They musical scores accompanying diagrams are written in a style resembling magic Cloud Script calligraphy."

(Tao: The Eastern Philosophy of Time and Change, by Philip Rawson and Laszlo Legeza)