Surya Siddhanta
विषुवच्छाययाम्यस् तद्विक्षेपाद् द्वादशोद्धृतात् । फलम् स्वनतनाडीघ्नम् स्वदिनार्धविभाजितम्॥
Multiply the latitude by the equinoctial shadow, and divide by twelve; the quotient multiply by the meridian-distance in nadis, and divide by the corresponding hall-day.
english translation
viSuvacchAyayAmyas tadvikSepAd dvAdazoddhRtAt । phalam svanatanADIghnam svadinArdhavibhAjitam॥
hk transliteration by Sanscript