form: word1word2, word2word1, word1word2word3, word3word2word1, word1word2word3; word2word3, word3word2, word2word3word4, word4word3word2, word2word3word4; ... That these methods have been effective, is testified to by the preservation of the most ancient Indian religious text, the (c. 1500 BCE), as a single text, without any variant readings. Similar methods were used for memorising mathematical texts, whose transmission remained exclusively oral until the end of the Vedic period (c. 500 BCE). The Sutra genre Mathematical activity in ancient India began as a part of a "methodological reflexion" on the sacred Vedas, which took the form of works called , or, "Ancillaries of the Veda" (7th–4th century BCE). The need to conserve the sound of sacred text by use of (phonetics) and chhandas (metrics); to conserve its meaning by use of (grammar) and nirukta (etymology); and to correctly perform the rites at the correct time by the use of kalpa (ritual) and (astrology), gave rise to the six disciplines of the . Mathematics arose as a part of the last two disciplines, ritual and astronomy (which also included astrology). Since the immediately preceded the use of writing in ancient India, they formed the last of the exclusively oral literature. They were expressed in a highly compressed mnemonic form, the sūtra (literally, "thread"): Extreme brevity was achieved through multiple means, which included using ellipsis "beyond the tolerance of natural language," using technical names instead of longer descriptive names, abridging lists by only mentioning the first and last entries, and using markers and variables. The sūtras create the impression that communication through the text was "only a part of the whole instruction. The rest of the instruction must have been transmitted by the so-called Guru-shishya parampara, 'uninterrupted succession from teacher (guru) to the student (śisya),' and it was not open to the general public" and perhaps even kept secret. The brevity achieved in a sūtra is demonstrated in the following example from the Baudhāyana Śulba Sūtra (700 BCE). The domestic fire-altar in the Vedic period was required by ritual to have a square base and be constituted of five layers of bricks with 21 bricks in each layer. One method of constructing the altar was to divide one side of the square into three equal parts using a cord or rope, to next divide the transverse (or perpendicular) side into seven equal parts, and thereby sub-divide the square into 21 congruent rectangles. The bricks were then designed to