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 text of the school of Buddhism known as Vijnanavada or Yogachara. The study of this scripture is essential preparation for anyone undertaking meditation exercise. Linking theory and praxis, the scripture offers a remarkably detailed and thorough course of study in both the philosophical and pragmatic foundation of Buddhist yoga, and their perfect, harmonious union in the realization of Buddhist enlightenment.