Surya Siddhanta
परमापक्रमाद् एवम् योजनानि विशोधयेत् । भूवृत्तपादाच् छेषाणि यानि स्युर् योजनानि तैः॥
Subtract from a quarter of the earth's circumference the number of yojanas thus derived from the greatest declination : at the distance of the remaining number of yojanas.
english translation