The four Tantras of Yoga

...it is of importance for the student of history and of religious origins to know that the Lamas recognize four chief classes of yogic Tantras, which may be briefly described as follows: (1) Tantras expository of the Thatness, or Ultimate Truth, and (2) of the Occult, or Mystic, Sciences; (3) the Yogini, or Shakti, Tantras; and (4) the Kalachakra Tantras.

 According to lamaic tradition, the first class had origin 'in the east' (which probably refers to eastern Bengal) in the time of King Rab-sal (Rab-gsal), who is believed to have flourished before the beginning of the Christian era. The second class arose through Nagarjuna and his followers during the second and third century of the Christian era, 'in the south' (which refers to Southern India). The third class, to which this Book and Book IV are related, is traceable to a learned teacher called Lawapa, of Urgyan (or Odyana), the ancient name of a region now comprised within the territory of Afghanistan, 'in the west' of India. It was Padma Sambhava, also of Urgyan, who first introduced and popularized among the Tibetans this class of Tantras. Padma Sambhava, otherwise known by his followers as Guru Rinpoch'e, the 'Precious Guru', is credited with having had eight Indian gurus belonging to eight different Schools of Buddhism. ... The fourth class, consisting of the Kalachakra Tantras, is said to have originated 'in the north', in Shambala, and to have been introduced into India about A.D. 600.

(From ''Tibetan Yoga and Secret Doctrines: Seven Books of Wisdom of the Great Path, according to the late Lama Kazi Dawa-Samdup's English rendering'' by W.Y. Evans-Wentz)