Brihat Samhita
प्रागर्धरात्रदृश्यो याम्याग्रः श्वेतकेतुरन्यश्च । क इति युगाकृतिरपरे युगपत्तौ सप्तदिनदृश्यौ ॥ ११-३७ ॥
Śveta Ketu is a comet which appears in the east about midnight with its tail pointing to the south. Ka Ketu is a comet of the shape of a carriage pole and appears in the west. Both the above Ketus are seen simultaneously for 7 days.
english translation
prAgardharAtradRzyo yAmyAgraH zvetaketuranyazca । ka iti yugAkRtirapare yugapattau saptadinadRzyau ॥ 11-37 ॥
hk transliteration by Sanscript