all thought of the world of multiplicity" in the advanced yogi who has completely uprooted his "network of Karma". He then enters the "fourth state", namely turiya or samadhi, beyond the usual states of waking, dreaming, and deep sleep, "that special thoughtless sleep, which consists of [just] consciousness." The 15th century Haṭha Yoga Pradīpikā goes further, stating (4.49) that "One should practice Khecarī Mudrā until one is asleep in yoga. For one who has achieved Yoganidrā, death never occurs." Khecarī Mudrā is the Hatha yoga practice of folding the tongue back so that it reaches inside the nasal cavity, where it can enable the yogi to reach samadhi. In the 17th century Haṭha Ratnāvalī (3.70), Yoganidrasana is first described. It is an asana or yoga pose where the legs are wrapped around the back of the neck. The text says that the yogi should sleep in this position, which "bestows bliss". These texts view yoganidra as a state, not a practice in itself. Modern usage Western "relaxationism" The yoga scholar Mark Singleton states that while relaxation is a primary feature of modern Western yoga, its relaxation techniques "have no precedent in the pre-modern yoga tradition", but derive mostly from 19th and 20th century Western "proprioceptive relaxation". This prescriptive approach was described by authors such as the "relaxationist" Annie Payson Call in her 1891 book Power through Repose, and the Chicago psychiatrist Edmund Jacobson, the creator of progressive muscle relaxation and biofeedback, in his 1934 book You Must Relax!. Dennis Boyes In 1973, Dennis Boyes published his book Le Yoga du sommeil éveillé; méthode de relaxation, yoga nidra ("The Yoga of Waking Sleep: method of relaxation, yoga nidra") in Paris, France. This is the first known usage of "yoga nidra" in a modern sense. In the book, Boyes makes use of relaxation techniques including the direction of attention to each part of the body: The French journal Revue 3e Millénaire, reviewing Boyes's approach in 1984, writes that Boyes proposes relaxation in order to "reach the state of emptiness". The person thus imperceptibly moves to a stage where relaxation becomes meditation, and can remain there once the mind's obsession with external objects or thoughts is removed. Satyananda In modern times, Satyananda Saraswati claimed to have experienced yoga nidra when he was living with his guru Sivananda Saraswati in Rishikesh. In 1976, he constructed a system of relaxation through guided meditation, which he