Yājñavalkya Śikṣā 147

147

jihvāmūle ca rephe ca vijñeyā capalā yathā
upadhmānīyasahitā puṣpiṇīṃ tāṃ vidurbudhāḥ

At the root of the tongue and in the sound r, [it] is to be known as capalā; / accompanied by the bilabial voiceless spirant, the wise know it as puṣpiṇī.