Flash rule: The Book of Silk is an ancient astronomy silk manuscript compiled by Chinese astronomers of the Western Han Dynasty. It lists 29 comets (referred to as 彗星, literally broom stars) that appeared over a period of about 300 years. There are roughly two dozen renderings of comets, some in fold out/pop-up format. In some cases, the pages of the document roll out to be five feet long. Each comet\'s picture has a caption which describes an event its appearance corresponded to, such as \"the death of the prince,\" \"the coming of the plague,\" or \"the three-year drought.\"