Mahā-vairocana-abhisaṃbodhi Tantra 

The ‘Tantra of the Awakening of Mahā-vairocana’, a highly influential caryā-tantra probably composed in the mid-7th century ce. It is possibly the earliest such work to systematically present the entire range of tantric practices with the exception of sexual yoga. It teaches the manner in which the enlightenment (saṃbodhi) of Mahā-vairocana is expressed in the world through various maṇḍalas, mantras, and mudrās so that practitioners may also achieve that state through the ritual cultivation of the practices assocated with them. Though this work was soon overshadowed in India by later tantric developments, it became extremely important in the east Asian transmission of esoteric Buddhism and is still highly revered in the Japanese Shingon school. Apart from a few Sanskrit fragments, the text has survived in Tibetan and Chinese translations together with several important commentaries that provide much information about early tantric practices and doctrines.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)