The Great Perfection, also known as the Atiyoga or Dzogchen (rDzogs chen), is a tradition of esoteric Buddhism that was first transmitted from India to Tibet in the Eighth Century of the Common Era. The Tantras translated in this volume were among the earliest translations into Tibetan, and are preserved in the manuscript collections known as the Hundred Thousand Tantras of the Ancients (rNying ma rgyud 'bum) and the Hundred Thousand Tantras of Vairochana (Vairo'i rgyud 'bum). The Tantra of the Nine Spaces clearly states that it was translated by Vairochana, a Tibetan monk who had gone to India in the Eighth Century in search of the teachings on instantaneous enlightenment, and Sri Singha, indicating that the translation was done while Vairochana was still in India with his guru. The Fish Wheel Tantra does not indicate who its translators were, but its inclusion in the Hundred Thousand Tantras of Vairochana is evidence that the Tibetan tradition held it to be the work of Vairochana. I have included the Tibetan texts of these works for your convenience and to help preserve this ancient literature. Many of the Tantras of the Great Perfection clearly state that they are intended for everyone to read, while some of them are declared to be very secret. The two Tantras translated in this volume are secret, and are not intended to be widely broadcast. The Fish Wheel Tantra states: "These are the oral transmissions from the remote caverns, the quintessence of quintessences of the teachings. If they are scattered about, the dakini Sri Jamunta will truly tear out our hearts." The Tantra of the Nine Spaces states: "Do not teach this to any three people. It is bequeathed to a single sure regent." We may be sure that these Tantras contain content that is most secret. These Tantras are not, however, like some of the secret Tantras found in the Buddhist and Hindu traditions that describe hidden sexual practices or feature elaborately coded mantras. On reading them, in fact, we might wonder why they are considered secret, as they do not advocate any transgressive practices of any kind. It is worth remembering that in the world these books were written the only way to get a book was to copy it from someone who had it. A guru who was in possession of books would evaluate someone very carefully before allowing them the opportunity to copy them or to have them copied. If the content of a book was such that problems might arise if it were misunderstood, the chances for a student to get it and copy it would be dramatically reduced. Such is the case with the books in this volume. The contents are such that they might easily be misunderstood, resulting in problems for the ones who had copies of them, and the loss of the books themselves. The world of books has changed dramatically since the rise of the printing press and the rise of values that favor freedom of information. We no longer have to fear that a book will be lost to the world if we loan it to a careless person. My own teacher, Dilgo Kyentse Rinpoche, published photo-offset editions of the Hundred Thousand Tantras of the Ancients, making them broadly available throughout the world. In translating and publishing these Tantras my intention is not to throw pearls before swine, but to make these works available to those students and teachers throughout the world who revere and take their contents seriously.