From The Art and Popular Culture Encyclopedia
Metaphysics and philosophy
The secretory activity of the pineal gland is only relatively understood. Historically, its location deep in the brain suggested to philosophers that it possessed particular importance. This combination led to its being a "mystery" gland with myth, superstition and occult theories surrounding its perceived function.
The notion of a 'pineal-eye' is central to the philosophy of the seminal French writer Georges Bataille, which is analyzed at length by literary scholar Denis Hollier in his study Against Architecture. In this work Hollier discusses how Bataille uses the concept of a 'pineal-eye' as a reference to a blind-spot in Western rationality, and an organ of excess and delirium. This conceptual device is explicit in his surrealist texts, The Jesuve and The Pineal Eye. (Bataille, G, Visions of Excess)
Helena Blavatsky and Alice Bailey, some of the earliest new age, theosophical occultists, have both written on spiritual and occult relationships concerning the pineal gland. This concept of an esoteric pineal-gland is directly addressed in a chapter of Alice Bailey's A Treatise on White Magic
It is thought to be critical to the function of the yogic posture, Khecarī mudrā.