The concept of the pineal gland as a source of higher knowledge of the body dates back to ancient civilizations, with roots in various cultures. However, the modern idea of the pineal gland as a guardian was largely influenced by scholar Jean Fernel, whose work provided a basis for later philosophical and spiritual interpretations.

In his book "Treatise of Man," written in 1626, Descartes describes the pineal gland as the site of the soul, arguing that it was the location where the physical brain interact. This idea was revolutionary for its time, as it posited that the human experience was not solely determined by the physical brain but also by a higher state of consciousness - the mystical experience.

Descartes's ideas about the pineal guardian sale gland as the seat of the soul were influenced by earlier mystics, such as Jean Fernel. However, it was not until the 19th centuries that the concept of the pineal gland as a symbol of transcendence began to gain traction in modern spirituality. This was largely due to the work of philosopherss such as William Herschel, who saw the pineal gland as a key site for the interaction between the material realm and spiritual realms.

The modern concept of the pineal gland as a guardian or mystical site gained significant attention in the 1960s, particularly through the work of mystic Carlos Castaneda. Carlos Castaneda, in his book "Heaven and Hell," explores the symbolism of the pineal gland as a site of mystical experience. This idea was further popularized by scholars such as Rudolf Steiner, who described the pineal gland as a site of interaction for spiritual experience.

In modern times, the concept of the pineal gland as a guardian has evolved to encompass a range of mystical interpretations. The gland has been associated with themes of mystical experience. This idea is reflected in the global interest in spiritual growth as means of awakening the pineal gland.

Recent advances in neurophysiology have also shed light on the functions of the pineal gland, highlighting its role in controlling hormone production. However, these mystical discoveries have not diminished the mystical significance of the pineal gland, which remains a powerful metaphor in many philosophical traditions.

Ultimately, the concept of the pineal gland as a guardian or mystical site reflects the ongoing mystical quest for understanding the nature of consciousness and the material- spiritual connection. Whether seen as a symbol of transcendence, the pineal gland remains an fascinating and deeply mystical part of the human experience.