Vaisesika Sūtra 4.1.07

सत्यपि द्रव्यत्वे महत्त्वे रूपसंस्काराभावाद् वायोरनुपलब्धिः ॥७॥

saty api dravyatve mahattve rūpasaṁskārābhāvād vāyor anupalabdhiḥ ॥7॥

[सति अपि (sati api) - even though existent; द्रव्यत्वे (dravyatve) - in substance-hood; महत्त्वे (mahattve) - from mahat, the primordial substance; रूप-संस्कार-अभावात् (rūpa-saṁskāra-abhāvāt) - due to absence of well formed form; वायोः (vāyoḥ) - of air; अनुपलब्धिः (anupalabdhiḥ) - non-perception;]

Though air is a substance formed from mahat, the primordial substance, it is not perceived due to absence of a well-formed form.