The Great Epic of the Bhārata dynasty 1.52.20

1.52.20

saptaśīrṣā dviśīrṣāśca pañcaśīrṣāstathāpare |
kālānalaviṣā ghorā hutāḥ śatasahasraśaḥ || 20 ||

"O Brahmana, thus I have recited the names of the principal snakes known widely for their achievements--I have not been able to name all, the number being countless. The sons of these snakes, the sons of those sons, that were burnt having fallen into the fire, I am unable to mention. They are so many! Some of three heads, some of seven, others of ten, of poison like unto the fire at the end of the yuga and terrible in form,--they were burnt by thousands!