The Māṇḍūkya Upaniṣad (, ) is the shortest of all the Upanishads, and is assigned to Atharvaveda. It is listed as number 6 in the Muktikā canon of 108 Upanishads. It is in prose, consisting of twelve short verses, and is associated with a Rig Vedic school of scholars. It discusses the syllable Aum; presents the theory of four states of consciousness; and asserts that Aum is Brahman – which is the Whole – and that Brahman is this self (ātman). The Mandukya Upanishad is notable for having been recommended in the Muktikā Upanishad, through two central characters of the Ramayana, as the one Upanishad that alone is sufficient for knowledge to gain moksha, and as sixth in its list of ten principal Upanishads. The text is also notable for inspiring Gaudapada's Mandukya Karika a classic for the Vedanta school of Hinduism. The Mandukya Upanishad is among the often cited texts on chronology and the philosophical relationship between Hinduism and Buddhism. Etymology The root of Mandukya is sometimes considered as Manduka (Sanskrit: मण्डूक) which has several meanings. Some of its meanings include "frog", "a particular breed of horse", "the sole of horse's hoof", or, "Spiritual distress" Some writers have suggested that "frog" is the etymological root for Mandukya Upanishad. Another root for the Upanishad's name is Mānduka (Sanskrit: माण्डूक) which literally is "a Vedic school" or means "a teacher". Paul Deussen states the etymological roots of Mandukya Upanishad to be a "half lost school of Rigveda". This school may be related to the scholar named Hrasva Māṇḍūkeya, whose theory of semivowels is discussed in Aitareya Aranyaka of Rigveda. Applying the rules of sandhi, the text is also called Mandukyopanishad. Chronology and authorship Chronology The chronology of Mandukya Upanishad, like that of other Upanishads, is uncertain and contested. The chronology is difficult to resolve because all opinions rest on scanty evidence, an analysis of archaism, style and repetitions across texts, driven by assumptions about likely evolution of ideas, and on presumptions about which philosophy might have influenced which other Indian philosophies. Several academics have dated the Mandukya Upanishad to the early centuries of the Common Era. The Japanese academic of Vedic, Hindu and Buddhist scriptures, Hajime Nakamura has dated the Mandukya Upanishad to "about the first or second centuries A.D." The scholar of South Asian religions, Richard E. King too has dated the Mandukya Upanishad at the first two centuries of