in the Hindu scriptures, occurs in verse 5.14.3 of the Brihadaranyaka Upanishad. The idea is also discussed in other early Upanishads. Gaudapada Gaudapada (ca. 7th century) was an early guru in the Advaita Vedanta. Gaudapada is traditionally said to have been the grand-guru of the great teacher, Adi Shankara, one of the most important figures in Hindu philosophy. Gaudapada is believed to be the founder of Shri Gaudapadacharya Math, and the author or compiler of the . Gaudapada wrote or compiled the , also known as the and as the . In this work, Gaudapada deals with perception, idealism, causality, truth, and reality. The fourth state, (turīya avasthā), corresponds to silence, as the other three correspond to AUM. It is the substratum of the other three states. It is, states Nakamura, atyanta-shunyata (absolute emptiness). Michael Comans disagrees with Nakamura's thesis that "the fourth realm (caturtha) was perhaps influenced by the Sunyata of Mahayana Buddhism." According to Comans, Comans further refers to Nakamura himself, who notes that later Mahayana sutras such as the Laṅkāvatāra Sūtra and the concept of Buddha-nature, were influenced by Vedantic thought. Comans concludes that Isaeva states that there are differences in the teachings in the texts of Buddhism and the Mandukya Upanishad of Hinduism, because the latter asserts that citta "consciousness" is identical with the eternal and immutable atman "soul, self" of the Upanishads. In other words, Mandukya Upanishad and Gaudapada affirm the soul exists, while Buddhist schools affirm that there is no soul or self. Adi Shankara Adi Shankara described, on the basis of the ideas propounded in the Mandukya Upanishad, the three states of consciousness, namely waking (jågrata), dreaming (svapna), and deep sleep (susupti),<ref group=web name=Om>[http://www.advaita.org.uk/discourses/downloads/om.pdf advaita.org.uk, ‘Om’ – three states and one reality (An interpretation of the Mandukya Upanishad)]</ref> which correspond to the three bodies: The first state is that of waking consciousness, in which we are aware of our daily world. "It is described as outward-knowing (bahish-prajnya), gross (sthula) and universal (vaishvanara)". This is the gross body. The second state is that of the dreaming mind. "It is described as inward-knowing (antah-prajnya), subtle (pravivikta), and burning (taijasa)". This is the subtle body. The third state is the state of deep sleep. In this state, the underlying ground of consciousness is undistracted. "[T]he Lord of all (sarv’-eshvara), the knower of all (sarva-jnya), the inner controller (antar-yami), the source of all (yonih sarvasya), the origin