This book contains translations of three Tantras on the Great Perfection (rDzogs chen). A Tantra is a sacred, and often esoteric, work of literature. The Great Perfection is held by its followers to be the highest pathway in the Buddhist tradition. The teachings these Tantras contain are considered so rare and precious that the first two, The Secret Wisdom of the Great Perfection and Clarity Equal to the Limit, clearly declare themselves to be secret. The third Tantra, on the other hand, Vajrasattva of the Great Sky, insists that it must be taught to anyone who wishes to study it. The Secret Wisdom of the Great Perfection in particular sets very definite limits on just who should be allowed to read it, and insists its distribution is to be limited, while The Great Sky of Vajrasattva demands that it be taught without limitation. All of these works are considered "Old Translations," and may date as far back as the 8th century of our era. They are retained in a compendium of manuscripts knows as The Hundred Thousand Tantras of the Old Ones, or rNying ma rgyud 'bum. The importance of this literature for historians, linguists, those who focus on the History of Ideas, scholars and practitioners of Buddhism, specialists in classical literature, and those who focus on esoteric tradations cannot be overestimated. The works contained herein also give us a window into the condition of Indian, Chinese, and Silk Route concerns of the period in which the Tang Dynasty was at its height and during which the Tibetan Empire was still strong.