Brahmanda Purana — Prakriya Pada, Shloka 1
Amāvasyā-Pitṛtarpaṇa: Purūravas and the Soma-Based Ancestral Offering (अमावस्या-पितृतर्पण / सोमतर्पण-विधि)
इति श्रीब्रह्माण्डे महापुराणे वायुप्रोक्ते पूर्वभागे द्वितीये ऽनुषङ्गपाद दारुवनप्रवेशभस्मस्नानविधिर्नाम सप्तविंशतितमो ऽध्यायः ऋषिरुवाच अगात्कथममावस्यां मासि मासि दिवं नृपः / ऐलः पुरूरवाः सूत कथं वातर्पयत्पितॄन्
iti śrībrahmāṇḍe mahāpurāṇe vāyuprokte pūrvabhāge dvitīye 'nuṣaṅgapāda dāruvanapraveśabhasmasnānavidhirnāma saptaviṃśatitamo 'dhyāyaḥ ṛṣiruvāca agātkathamamāvasyāṃ māsi māsi divaṃ nṛpaḥ / ailaḥ purūravāḥ sūta kathaṃ vātarpayatpitṝn
Thus, in the Śrī Brahmāṇḍa Mahāpurāṇa, in the earlier section spoken by Vāyu, in the second part, is the twenty-seventh chapter called “Anuṣaṅgapāda: the entry into the Dāru forest and the rite of bathing with sacred ash.” The ṛṣi said: “O king, how did he go to heaven month after month on the new-moon day (amāvasyā)? O Sūta, how did Aila Purūravas satisfy the Pitṛs with tarpaṇa?”