To age with the sun and moon and be renewed by spring and summer, to conserve the seeds of growth in autumn and winter and to be nourished by the eternal breath of the Tao--these are the goals of the Taoist alchemists, the masters of the arts of health, longevity, and immortality. This book is a translation of a concise Taoist alchemical manual known as the Dragon-Tiger Classic, along with its two most important commentaries. The classic, written in ancient times by an unknown author and published during the fifteenth century BCE, is regarded by contemporary Taoist practitioners as the most complete guide to spiritual transformation. It covers the three forms of Taoist practice:    *  External alchemy, concerned with the ingestion of minerals, herbs, and other substances to attain health, longevity, and immortality    *  Sexual alchemy, in which the practitioner uses the energy of a sexual partner to cultivate his or her own energy    *  Internal alchemy, the practice of meditation, calisthenics, and yogic postures to cultivate mind and body An extensive introduction by the translator and the inclusion of two commentaries by traditional Chinese authors aid the reader in understanding this concise, symbolic text.