The word yoga has many meanings, including "meditation," "method," and "union." While the physical exercises of Hindu yoga are familiar to Westerners, the subtle metaphysics and refined methods of spiritual development that characterize Buddhist yoga are not yet well known. This volume presents a landmark translation of a classical sourcebook of Buddhist yoga, the Sandhinirmochana-sutra, or "Scripture Unlocking the Mysteries," a revered scripture of the school of Buddhism known as Vijnanavda or Yogachara. The study of this scripture is considered essential preparation for anyone undertaking an in-depth commitment to meditation practice, as it reveals the keys to the genuine practice and authentic realization of Buddhism at its most complete and sophisticated levels.