Brihat Parashara Hora Shastra
राशीन् विहाय खेटस्य द्विघ्नमंशाद्यमर्कहृत्। शेषं सैकं तद्राशेर्भपाः षष्ट्यंशापाः स्मृताः॥ ३३॥
Shashtiāńś (1/60th part of a Rāśi, or half a degree each). To calculate the Shashtiāńś Lord ignore the Rāśi position of a Grah and take the degrees etc. it traversed in that Rāśi. Multiply that figure by 2 and divide the degrees by 12. Add 1 to the remainder, which will indicate the Rāśi, in which the Shashtiāńś falls.
english translation
rAzIn vihAya kheTasya dvighnamaMzAdyamarkahRt। zeSaM saikaM tadrAzerbhapAH SaSTyaMzApAH smRtAH॥ 33॥
hk transliteration by Sanscript