Surya Siddhanta
ध्रुवोन्नतिर् भचक्रस्य नतिर् मेरुम् प्रयास्यतः। निरक्षाभिमुखम् यातुर् विपरीते नतोन्नते॥
As we move more and more towards the Merus we can see the pole-star (Dhruva) is elevated more and more and the circle of constellations (bhacakra* ) is depressed more and more. The reverse happens, that is, depression of pole star and elevation of circle of constellations, when one moves more and more towards the place of no latitude.
english translation