This book is a unique attempt by historians, anthropologists and specialists of different religions and esoteric trends to investigate the mental and physical 'techniques' for obtaining an 'experience' of the Absolute or the Sacred. Cognitive techniques include prayers or litanies practised in different ways, through repetition (Sufi dhikr, Christian Hesychasm, yoga) or motion (Sufi dance), along with visualizations (in Kabbala, Sufism, Buddhism) or breathing exercises (in many trends), and in the invocation of names (Kabbala, Sufism). Such techniques may also be taught by spirits or immaterial entities (Daoism, shamanism). Physical techniques aim to establish the practical conditions for controlling the body and preventing it from becoming an obstacle on the ascetic path. They include body postures in yoga and, most particularly, seclusion, often performed in solitary places (a forty-day retreat in Sufism or the famous three-year seclusion in a cave or hermitage in the case of Tibetan Buddhism). Mental and physical techniques are obviously intimately associated, and this book underlines the similarities between their practice in most world religions, the main points in common being the exercises based on repetition, breathing techniques and seclusion. In addition, some authors emphasize the fact that certain mystic trends, like Christian Hesychasm ('prayer of Jesus'), Sufism and Kabbala have borrowed spiritual techniques from Buddhism, and especially from yoga, and that such loans have also taken place between Sufism and Kabbala, and Buddhism and Daoism.