Clairvoyance is an alleged psychic ability to see things beyond the range of the power of natural vision.

R. T. Carroll. "Clairvoyance". The Skeptic's Dictionary (19 Sep, 2012) []

An early case of clairvoyance is credited to the Marquis de Puységur, a follower of Franz Mesmer, who in 1784 treated a peasant named Victor Race. During treatments, Race would go into trance and undergo a personality change. He would become fluent and articulate, and would even diagnosis his own ailments as well as those of others.

Taves, Ann. Fits, Trances, and Visions: Experiencing Religion and Explaining Experience from Wesley to James. (Princeton: Princeton University Press, 1999) p. 126.