Sanskrit kalacakram: Wheel of Time
A very extensive seventh-century work that attempts to describe all phenomena of the world in an all-inclusive vision. The outer section deals with cosmology and natural sciences such as astronomy, geography and engineering.
The inner section, the more secret part of the text, describe the human body and mind, the functions of the nadi, six types of meditation practice, and contain visualizations concerning the use and flow of s.exual energy.
According to Edwin Bernbaum and his The Way to Shambhala,
the text teaches, for example, that male semen and menstrual flow
carry the impulse to enlightenment and can
spread bliss throughout the body, transforming it into a vehicle to liberation (Bernbaum, p.124).
The Kalachakra Tantra and its associated rituals also laid the basis for the Tibetan calendar, which started in 946, and is said to have originated in India at least 300 years before it reached Tibet. The work also contains some of the teachings that later became part of the famous ‘Six Doctrines of Naropa’ or Naro Chos-drug.