A purification ceremony known as "misogi" involves the use of fresh water, salt water, or salt to remove "kegare". Full immersion in the sea is often regarded as the most ancient and efficacious form of purification. This act links with the mythological tale in which Izanagi immersed himself in the sea to purify himself after discovering his deceased wife; it was from this act that other kami sprang from his body. An alternative is immersion beneath a waterfall. Salt is often regarded as a purifying substance; some Shinto practitioners will for instance sprinkle salt on themselves after a funeral, while those running restaurants may put a small pile of salt outside before business commences each day. Fire, also, is perceived as a source of purification. The "yaku-barai" is a form of harae designed to prevent misfortune, while the "oharae", or "ceremony of great purification", is often used for end-of-year purification rites, and is conducted twice a year at many shrines. Before the Meiji period, rites of purification were generally performed by onmyōji, a type of diviner whose practices derived from the Chinese yin and yang philosophy.