Coin vanish is a generic term for any technique employed by magicians to create the illusion of causing a coin to vanish from one's hand. A variety of methods exist for effecting such a vanish, most involving sleight of hand, and many taking advantage of an optical principle called retention of vision. Some sleight-of-hand coin vanishes can be combined with sleeving, allowing the magician to show both hands as being empty at the same time. Methods employing mechanical aids can also be used, including Chuck Leach's The Raven and John Cornelius' Fickle Nickel. These devices reduce, if not entirely eliminate, the need for sleight of hand, but often require a degree of digital dexterity.