Srimad-Bhagavatam: Canto 5 - Chapter 1 - Verse 31
Sanskrit:
ततोऽधस्तात्पाताले नागलोकपतयो वासुकिप्रमुखा: शङ्खकुलिकमहाशङ्खश्वेतधनञ्जयधृतराष्ट्रशङ्खचूडकम्बलाश्वतरदेवदत्तादयो महाभोगिनो महामर्षा निवसन्ति येषामु ह वै पञ्चसप्तदशशतसहस्रशीर्षाणां फणासु विरचिता महामणयो रोचिष्णव: पातालविवरतिमिरनिकरं स्वरोचिषा विधमन्ति ॥ ३१ ॥
ITRANS:
tato ’dhastāt pātāle nāga-loka-patayo vāsuki-pramukhāḥ śaṅkha-kulika-mahāśaṅkha-śveta-dhanañjaya-dhṛtarāṣṭra-śaṅkhacūḍa-kambalāśvatara-devadattādayo mahā-bhogino mahāmarṣā nivasanti yeṣām u ha vai pañca-sapta-daśa-śata-sahasra-śīrṣāṇāṁ phaṇāsu viracitā mahā-maṇayo rociṣṇavaḥ pātāla-vivara-timira-nikaraṁ sva-rociṣā vidhamanti.
Translation:
Beneath Rasātala is another planetary system, known as Pātāla or Nāgaloka, where there are many demoniac serpents, the masters of Nāgaloka, such as Śaṅkha, Kulika, Mahāśaṅkha, Śveta, Dhanañjaya, Dhṛtarāṣṭra, Śaṅkhacūḍa, Kambala, Aśvatara and Devadatta. The chief among them is Vāsuki. They are all extremely angry, and they have many, many hoods — some snakes five hoods, some seven, some ten, others a hundred and others a thousand. These hoods are bedecked with valuable gems, and the light emanating from the gems illuminates the entire planetary system of bila-svarga.