Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 2
सहस्रशिरस: पुंसो नाभिह्रदसरोरुहात् ।जातस्यासीत् सुतो धातुरत्रि: पितृसमो गुणै: ॥ २ ॥
sahasra-śirasaḥ puṁsonābhi-hrada-saroruhātjātasyāsīt suto dhāturatriḥ pitṛ-samo guṇaiḥ
Lord Viṣṇu [Garbhodakaśāyī Viṣṇu] is also known as Sahasra-śīrṣā Puruṣa. From the lake of His navel sprang a lotus, on which Lord Brahmā was generated. Atri, the son of Lord Brahmā, was as qualified as his father.