Śaiśirīya Śikṣā 23

23

sparśānāṃ karaṇaṃ spṛṣṭamantasthāsvīṣaducyate
svarāṇāmūṣmaṇāṃ caiva vivṛtaṃ karaṇaṃ smṛtam

The articulatory effort of stop consonants is contacted; for semivowels it is said to be slightly [contacted]; / and the articulatory effort of vowels and spirants is remembered as open.