The Nadabindu Upanishad is an ancient Sanskrit text and one of the minor Upanishads of Hinduism. It is one of twenty Yoga Upanishads in the four Vedas. It also known as Amrita Nada Bindu Upanishad. The text exists in two significantly different versions, the North Indian and the South Indian. These manuscripts are respectively attached to the Atharvaveda, or to the Rigveda The word Nada, being a Vedic terminology refers to as the unstruck sound or "Anahata Nada" which is reported as a thin buzzing sound being heard in right ear, and upon whom meditating, a person attains the "turya" of meditation easily. It is said that this sound has its source in the Anahata Chakra( the fourth Chakra in vedic terminology). Other religions also have same terms for it like "shabad", "Word" etc. This scripture tells how to listen to that sound so that to attain a deep state of meditation. The relative chronology of the text is placed by Mircea Eliade with the ancient Yoga Upanishads. He suggests that it was composed in the same period when the following texts were composed – Maitri Upanishad, the didactic parts of the Mahabharata, the chief Sannyasa Upanishads and along with other early Yoga Upanishads such as Brahmabindu, Brahmavidya, Tejobindu, Yogatattva, Kshurika, Yogashikha, Dhyanabindu and Amritabindu. These and the Nadabindu text, were composed earlier than the ten or eleven later yogic Upanishads such as the Yoga-kundali, Varaha and Pashupatabrahma Upanishads. Gavin Flood dates this text, along with other Yoga Upanishads, to be probably from the 100 BCE to 300 CE period. Guy Beck dates it to be probably from the pre-Christian era and the earliest document on the Yoga of sacred sound, while Georg Feuerstein suggests that the text is likely from a period in early 1st millennium CE. Mikel Burley states that this text does not provide techniques of Hatha Yoga, but probably influenced the later Hatha yoga texts. The Upanishad is also referred to as Nadabindu Upanishad or Nadabindupanisad. It is listed at number 38 in the serial order of the Muktika enumerated by Rama to Hanuman in the modern era anthology of 108 Upanishads. In the Colebrooke's version of 52 Upanishads, popular in north India, it is listed at number 17. The Narayana anthology also includes this Upanishad at number 17 in Bibliothica Indica. In the collection of Upanishads under the title "Oupanekhat", put together by Sultan Mohammed Dara Shikoh in 1656, consisting of a Persian translation of 50 Upanishads and who prefaced it as the best book on religion, the Amratanada is listed at number 43 and is named anbratnad. Know the Atman as one, Then, waking, dream and deep sleep, Throwing off these three states, You will never be born again. A single being-self there is, It dwells in each and every being, Uniform and yet multiform, It appears like the moon in pond. —Brahmabindu Upanishad 11–12