Ati Yoga (shin tu rnal 'byor)
Ati Yoga (or Primordial Yoga), which is another name for the Tibetan tradition of Dzogchen, employs an Adi-Buddha sadhana, or practice. NB: Ati and Adi are different orthographic representations of phonemes of the language of Uddiyana which equate to 'primordial' according to Chögyal Namkhai Norbu.
The third of the Three Inner Tantras. It emphasizes, according to Jamgon Kongtrul the First, the view that liberation is attained through growing accustomed to insight into the nature of primordial enlightenment, free from accepting and rejecting, hope and fear. The more common word for Ati Yoga nowadays is 'Dzogchen.' The Ati Yoga teachings first appeared in this world to Garab Dorje in the country of Uddiyana to the west of India.
According to The Narration of the Precious Revelation of the Terma Treasures by Longchen Rabjam (p. 87-88), the great master Padmasambhava described the teaching of Ati Yoga in the following way before imparting them to Yeshe Tsogyal:
"It is an instruction unlike any I have given in the past, the summit that transcends all of the nine gradual vehicles. By seeing its vital point, mind-made views and meditations are shattered. The paths and levels are perfected with no need for struggle. Disturbing emotions are liberated into their natural state without any need for reform or remedy. This instruction brings realization of a fruition within oneself that is not produced from causes. It instantly brings forth spontaneously present realization, liberates the material body of flesh and blood into the luminous sambhogakaya within this very lifetime, and enables you to capture the permanent abode, the precious dharmakaya realm of spontaneous presence, within three years, in the domain of Akanishtha. I possess such an instruction and I shall teach it to you!"
Ati Yoga is a synonym for Great Perfection and Dzogchen.
Dzogchen (rdzogs pa chen po, Skt. mahasandhi). Also known as Great Perfection and Ati Yoga. The highest teachings of the Nyingma School of the Early Translations. In this world the most well known human lineage masters are: Garab Dorje, Manjushrimitra, Shri Singha, Jnanasutra, Vimalamitra, Padmasambhava and Vairotsana. Dzogchen has two chief aspects: the lineage of scriptures and the lineage of teachings (dpe brgyud dang bka’ brgyud). The scriptures are contained in the tantras of the Three Sections of Dzogchend Section, Space Section and Instruction Section. The first two were brought to Tibet chiefly by Vairotsana while the Instruction Section was mainly transmitted by Vimalamitra and Padmasambhava. In addition, numerous Dzogchen termas were concealed by these masters and revealed through the following centuries. The lineage of teachings is embodied in the oral instructions one receives personally from a qualified master and holder of the Dzogchen lineage. The Tibetan historian Guru Tashi Tobgyal elaborates in his Ocean of Wondrous Sayings about Padmasambhava’s specific lineage of Dzogchen in the following way: “The great master is of the same nature as the infinite number of buddhas of the three kayas and does therefore not depend upon the concept of linear transmission. He is indivisible from the buddhas and the pure realms of the three kayas. However, in accordance with how other people perceive, Padmasambhava is not only the master of the numberless tantras of Vajrayana but possesses a unique short lineage of mastery over the profound topics of Nyingtig, the Luminous Great Perfection of the definitive meaning, entrusted to him by the three masters Garab Dorje, Manjushrimitra and Shri Singha. In particular, Padmasambhava acted upon a prophesy from Vajra Varahi and then received detailed teachings from Shri Singha.
Ati Yoga (shin tu rnal 'byor). The third of the Three Inner Tantras. According to Jamgon Kongtrul the First, it emphasizes the view that liberation is attained through growing accustomed to insight into the nature of primordial enlightenment, free from accepting and rejecting, hope and fear. The more common word for Ati Yoga nowadays is 'Dzogchen,' the Great Perfection. Ati means 'supreme.'
from the Glossary in The Lotus-Born, 1993