Verse 18

भावयत्यनिलस्पन्दं स्पर्शबीजरसोन्मुखम् ।ताभ्यामाकाशवाताभ्यामदृष्टाभ्यां मनोदृशा

In plain words

conceives the vibration of wind, inclined toward the seed-essence of touch. From those two, ākāśa and wind — unseen, [grasped] by the mind's eye —