The Astronomical Observatories of Jai Singh c15.s1.t6.12

c15.s1.t6.12

"(1) On a stony surface, made water level, or upon hard plaster, made level, there draw an even circle of a radius equal to any required number of digits of the gnomon. (2) At its centre set up the gnomon of twelve digits of the measure fixed upon; and, where the extremity of its shadow touches the circle in the former and after parts of the day, (3) fixing two points upon the circle, and calling them the forenoon and afternoon points, draw midway between them, by means of a fish figure, a north and south line. (4) Midway between the north and south directions draw, by a fish figure, an east and west line: and, in like manner, also by the fish figures, between the four cardinal directions, draw the intermediate directions. (5) Draw a circumscribing square, by meansof the lines going out from the centre: by the digits of its base lines projected upon that, is any given shadow reckoned. (6) The east and west line is called the prime vertical (*sama-maṇḍala*): it is likewise denominated the east and west hour circle (*unmaṇḍala*), and the equinoctial circle (*viṣuvan maṇḍala*). (7) Draw likewise an east and west line through the equinoctial shadow (*viṣuvad-bhā*); the interval between any given shadow and the line of the equinoctial shadow is denominated the measures of the amplitude¹ (*agrā*).”