Tantras (Buddhism) in the context of "Adi-Buddha"

Sanskrit Buddhist literature refers to Buddhist texts composed either in classical Sanskrit, in a register that has been called "Buddhist Hybrid Sanskrit" (also known as "Buddhistic Sanskrit" and "Mixed Sanskrit"), or a mixture of these two. Several non-Mahāyāna Nikāyas appear to have kept their canons in Sanskrit, the most prominent being the Sarvāstivāda school. Many Mahāyāna Sūtras and śāstras also survive in Buddhistic Sanskrit or in standard Sanskrit.

During the Indian Tantric Age (8th to the 14th century), numerous Buddhist Tantras were written in Sanskrit, sometimes interspersed with local languages like Apabhramśa, and often containing notable irregularities in grammar and meter.

Luminous mind (Skt: prabhāsvara-citta or ābhāsvara-citta, Pali: pabhassara citta; Tib: འོད་གསལ་གྱི་སེམས་ ’od gsal gyi sems; Ch: 光明心 guangmingxin; Jpn: 光明心 kōmyōshin) is a Buddhist term that appears only rarely in the Pali Canon, but is common in the Mahayana sūtras and central to the Buddhist tantras. It is variously translated as "brightly shining mind" or "mind of clear light", while the related term luminosity (Skt. prabhāsvaratā; Tib. འོད་གསལ་བ་ ’od gsal ba; Ch. guāng míng; Jpn. kōmyō; Kor. kwangmyōng) is also translated as "clear light" or "luminosity" in Tibetan Buddhist contexts or "purity" in East Asian contexts.

The Theravada school identifies the "luminous mind" with the bhavanga, a concept first proposed in the Theravāda Abhidhamma. The later schools of the Mahayana identify it with bodhicitta and tathagatagarbha. The luminosity of mind is of central importance in the philosophy and practice of the Buddhist tantras, Mahamudra, and Dzogchen.

Tibetan tantric practice, also known as "the practice of secret mantra", and "tantric techniques", refers to the main tantric practices in Tibetan Buddhism. The great Rime scholar Jamgön Kongtrül refers to this as "the Process of Meditation in the Indestructible Way of Secret Mantra" and also as "the way of mantra", "way of method" and "the secret way" in his Treasury of Knowledge. These Vajrayāna Buddhist practices are mainly drawn from the Buddhist tantras and are generally not found in "common" (i.e. non-tantric) Mahayana. These practices are seen by Tibetan Buddhists as the fastest and most powerful path to Buddhahood.

In Tibetan Buddhism, the higher tantric yogas are generally preceded by preliminary practices (Tib. ngondro), which include sutrayana practices (i.e. non-tantric Mahayana practices) as well as preliminary tantric meditations. Tantric initiation is required to enter into the practice of tantra.

Classes of Tantra in Tibetan Buddhism refers to the categorization of Buddhist tantric scriptures in Indo-Tibetan Buddhism. Tibetan Buddhism inherited numerous tantras and forms of tantric practice from medieval Indian Buddhist Tantra. There were various ways of categorizing these tantras in India. In Tibet, the Sarma (New Translation) schools categorize tantric scriptures into four classes, while the Nyingma (Ancients) school use six classes of tantra.

The Āryamañjuśrī­mūlakalpa (The Noble Root Manual of the Rites of Mañjuśrī) is a Mahāyāna sūtra and a Mantrayāna ritual manual (kalpa) affiliated with the bodhisattva of wisdom, Mañjuśrī. In Tibetan Buddhism it is classified as a Kriyā-tantra. According to Sanderson (2009: 129) and the study by Matsunaga (1985), the text is datable to about 775 CE.

The Mañjuśrīmūlakalpa is often cited as the earliest example of an extant Indian Buddhist Tantra. Some scholars identify it as a compilation of a core verse text dated circa 6th century CE with later accretions and additions. The Sanskrit version, significantly longer than its corresponding Chinese and Tibetan renderings, is still extant.