Brihat Samhita
इन्दुअर्कमण्डलऽकृतिरसितत्वात्किल न दृश्यते गगने । अन्यत्र पर्वकालाद्वरप्रदानात्कमलयोनेः ॥ ५-०२ ॥
That he has a disc like the sun and moon and as that disc is black it is invisible when in the sky except on the occasion of eclipses in virtue of a boon from Brahmā.
english translation
induarkamaNDala'kRtirasitatvAtkila na dRzyate gagane । anyatra parvakAlAdvarapradAnAtkamalayoneH ॥ 5-02 ॥
hk transliteration by Sanscript