"The first stage in guidance is an initiation into a specific mantra... The word mantra means that which liberates the mind from all griefs, sorrows and agonies. A mantra consists of one or more words chosen specifically for leading a particular aspirant to the final Truth. Not every word can be a mantra. Mantras are not composed by the initiator. They have been handed down to him through his tradition, having been revealed to great Yogis and Seers while they were in a superconscious state. The science of mantra is very exact, but very few people know or understand its significance. Once initiated the disciple repeats and meditates upon his mantra throughout his life. And gradually the mantra leads him to the stage of samadhi." – Swami Rama, Lectures on Yoga.
Much scientific research has been done on (1) sleep and (2) yoga and related practices of relaxation and meditation methods. One of the neglected areas of research is what is known in the yoga circles as yoga-nidra, that is, yoga-sleep.