In the early 1960s, Lilly was introduced to psychedelic drugs such as LSD and began a series of experiments in which he ingested a psychedelic drug either in an isolation tank or in the company of dolphins. These events are described in his books "Programming and Metaprogramming in the Human Biocomputer", published in 1968, and "The Center of the Cyclone", published in 1972. Following advice from Ram Dass, Lilly studied Patanjali's system of yoga (finding I. K. Taimni's "Science of Yoga", a modernized interpretation of the Sanskrit text, most suited to his goals). He also paid special attention to self-enquiry meditation advocated by Ramana Maharshi, and reformulated the principles of this exercise with reference to his human biocomputer paradigm (described in "Programming and Metaprogramming in the Human Biocomputer: Theory and Experiments" and "The Center of the Cyclone").