Yājñavalkya Śikṣā 189

189

raṅge caiva samutpanne na grāhyaṃ pūrvamakṣaram
svaraṃ dīrghaṃ prayuñjīta paścānnāsikyamācaret

When nasalised vowel colouring arises, the preceding syllable is not to be grasped [as short]; / one should employ a long vowel, and afterwards perform the nasal sound.