Mysticism is the belief in, or experience of, a reality surpassing normal
 human understanding or experience. This is especially so of a reality
 perceived as being essential to the nature of life.

Tantric practices can be regarded as mystical in nature.

At the beginning of the 20th century a gentleman named Aleister
 Crowley researched the ways by which a state of possession could
 be achieved through sensual means. He made a detailed study of
 Indian mysticism and tantric practices, and used a technique to induce
 a sexual trance, which he called "Eroto-comatose Lucidity".