Sāyaṇa (सायण, with honorific Sāyaṇācārya ; died 1387) was an important commentator on the Vedas. He flourished under King Bukka I and his successor Harihara II, in the Vijayanagar Empire of South India.
Sayana's major work is his Vedartha Prakasha (literally, "the meaning of the Vedas made manifest"), or commentary on the Vedas. His commentary on the Rigveda was edited by Max Müller, 1823-1900. The core portion of the commentary was likely written by Sayana himself, but it also includes contributions of his brother Mādhava, and additions by his students and later authors who wrote under Sayana's name. "Sayana" (or also Sāyaṇamādhava) by convention refers to the collective authorship of the commentary as a whole without separating such layers.
He has also written many lesser manuals called Sudhanidhis treating Prayaschitta (expiation), Yajnatantra (ritual), Purushartha (aims of human endeavour), Subhashita (Collection of moral sayings), Ayurveda (Indian traditional medicine), Sangit Sara (The essence of music), Prayaschitra, Alankara, and Dhatuvrddhi (grammar)
Strictly speaking, Sayana here attributes a (fantastically high) speed to the Sun (Surya), not to light itself. Depending on what values one assumes for a yojana and for a nimesha, this speed corresponds to about 186,000 miles per second, roughly equal to the speed of light.
1 yojana is said to comprise either 4 or 8 krosha (a cry or shout, or the range of the voice in calling); and 1 krosha (or goruta ~ as far as a cow’s lowing may be heard, or a bull’s roar) may represent either 1000 or 2000 daNDa (a rod or staff), and 1 danda represents 1 pauruSa (a man’s length) which equals 1 dhanvantara (bow-string) or dhanu (bow). 1 yojana measures either 4,000 or (more likely) 8,000 dhanus. Assuming that 1 paurusha is 6 ft long, then 1 yojana must represent a distance of about 14.6 km (or about 9 miles, as suggested by Monier-Williams).
nimesa means shutting the eye or winking, and as a measure of time it is a wink of the eye or a moment. The Arthashastra (c. 300 BC) defines 1 nimesa as 1/360,000th of a day and night, i.e. 0.24 seconds.
Given that 1 yojana is between 14.6 and 16.4 km, 2,202 yojanas must represent between 32,149 and 36,113 km. Half a nimesha is 0.12 seconds. Sayana thus gives the "speed of the Sun" as between 267,910 and 300,940 km/sec, i.e. the same order of magnitude as the speed of light at 299,792 km/sec.
Sayana's commentary is still 300 years older than the first known successful measurement of the speed of light. Kak points out that the Vayu Purana (ch. 50) has a comparable passage, where the "speed of the Sun" is exactly 1/18th of Sayana's value. While he is also susceptible to assuming "scientific foreknowledge" by mystical means, he also accepts that "to the rationalist" the proximity of Sayana's value to the physical constant is simply coincidence.
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