Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 6
रेत: सिषिचतु: कुम्भे उर्वश्या: सन्निधौ द्रुतम् ।रेवत्यां मित्र उत्सर्गमरिष्टं पिप्पलं व्यधात् ॥ ६ ॥
retaḥ siṣicatuḥ kumbheurvaśyāḥ sannidhau drutamrevatyāṁ mitra utsargamariṣṭaṁ pippalaṁ vyadhāt
Upon seeing Urvaśī, the celestial society girl, both Mitra and Varuṇa discharged semen, which they preserved in an earthen pot. The two sons Agastya and Vasiṣṭha later appeared from that pot, and they are therefore the common sons of Mitra and Varuṇa. Mitra begot three sons in the womb of his wife, whose name was Revatī. Their names were Utsarga, Ariṣṭa and Pippala.
Modern science is trying to generate living entities in test tubes by processing semen, but even long, long ago it was possible for semen kept in a pot to develop into a child.