Surya Siddhanta
भूमण्डलात् पञ्चदशे भागे देवे +अथ वासुरे। उपरिष्टाद् व्रजत्य् अर्कः सौम्ययाम्यायनान्तगः॥
The sun passes directly overhead in the 15th part of the circumference of earth during his northern motion (uttara ayana) in the hemisphere of demigods (devabhaga) and his southern motion (dakshiëayana) in the hemisphere of demons (asurabhaga).
english translation