The mythical unicorn is a horselike animal with a single horn in the middle of its forehead. Unicorns were first described by Ctesias, the Greek historian and physician, in about 400 BCE. According to legend, the only person who can catch a unicorn is a virgin. Unicorns were said to be able to detect poison by dipping their horns into any suspect food or drink. A unicorn is safe if it jumps into a virgin's lap while being pursued. Because of this, the Virgin Mary is often depicted with a unicorn in her lap, to symbolize the Immaculate Conception. The unicorn symbolizes purity and goodness. It also traditionally represents a large and happy family. In China, this meant many sons, and the unicorn is sometimes shown in Chinese art with a young boy on its back. To dream of a unicorn is a sign of many pleasant family activities. If a young woman dreams of a unicorn, it indicates a son in her near future.