Compressing his breathings let him, who has subdued all motions, breathe forth through the nose with gentle breath. Let the wise man without fail restrain his mind, that chariot yoked with vicious horses.

In plain words: The meditator should control his breathing, keep his body still, and breathe out gently through the nose. The mind is like a chariot pulled by wild horses, so a wise person must always keep a firm hold on it.