Surya Siddhanta
कर्क्यादौ प्रोज्झ्य चक्रार्धात् तुलादौ भार्धसम्युतात् । मृगादौ प्रोज्झ्य भगणान् मध्याह्ने +अर्कः स्फुटो भवेत्॥
And when the Sun is in the fourth quarter of the Ecliptic subtract the signs &c. (which compose the arc) from 12 signs; the remainder will be the true longitude of the Sun at noon. (To the longitude, just found, apply the amount of the precession of the equinoxes inversely for the Sun's true place.) (In order to find the mean place of the Sun from his true place above found,) find the 1st equation from the true place of the Sun and apply it inversely to the place repeatedly, the result is the mean place of the Sun (that is, assume the true place as his mean place, find the Sun's first equation from it and add this equation to the true place if the equation be subtractive, but if it be additive, subtract it from the true place; the result will be somewhat nearer to the exact mean place of the Sun at the given noon; assuming this result as the Sun's mean place apply the said mode of calculation, and repeat the process until you get the exact mean place of the Sun).
english translation
karkyAdau projjhya cakrArdhAt tulAdau bhArdhasamyutAt । mRgAdau projjhya bhagaNAn madhyAhne +arkaH sphuTo bhavet॥
hk transliteration by Sanscript