Surya Siddhanta
भुक्तियोजनजा सङ्ख्या सेन्दोर् भ्रमणसङ्गुणा । स्वकक्षाप्ता तु सा तस्य तिथ्याप्ता गतिलिप्तिका॥
Multiplying this number of yojanas of daily motion (bhuktiyojanä) by the orbit of the moon and dividing it by the (planet’s) own orbit will yield their daily motions in kaläs (gatikalä).
english translation