The French philosopher René Descartes (1596-1650) dedicated much time to the study of the pineal gland, as can be seen from this sketch. He called it the “principal seat of the soul” and believed the pineal was the point of connection between the intellect and the body.
An article in New Dawn magazine (Special Issue Vol 6 No 4) titled Mystery of the Pineal Gland Finally Revealed? by Anthony Peake uses this diagram and shares some very interesting insights. In particular, information about Biophotons, how living things emit small quantites of light. Peake suggests that Biophotons are what the third eye (the pineal gland) sees in dream states and during Near-Death Experiences. Examples are when people who have been blind from birth have a Near-Death Experience and actually see their body from the outside and follow a light down a tunnel.