Surya Siddhanta
कक्षा भूकर्णगुणिता महीमण्डलभाजिता। तत्कर्णा भूमिकर्णोना ग्रहोच्च्यम् स्वम् दलीकृताः॥
Multiplying the (planet’s) own orbit by the diameter of the earth (bhukarëa) and dividing by the earth’s circumference will give the (planet’s) own orbital diameter (karëa). When the diameter of the earth (bhukarëa) is subtracted from this and the result is divided by two, the distance from the earth is found.
english translation