Institutio Oratoria

The best effect is produced by letting the motion of the hand start from the left and end on the right, but this must be done gently, the hand sinking to rest and avoiding all appearance of giving a blow, although at the end of a sentence it may sometimes be allowed to drop, but must quickly be raised again: or it may occasionally, when we desire to express wonder or dissent, spring back with a rapid motion. In this connexion the earlier instructors in the art of gesture rightly added that the movement of the hand should begin: and end with the thought that is expressed. Otherwise the gesture will anticipate or lag behind the voice, both of which produce an unpleasing effect.

Some, through excess of subtlety, have erroneously prescribed that there should be an interval of three words between each movement; but this rule is never observed, nor can it be. These persons, however, were desirous that there should be some standard of speed or slowness (a most rational desire), with a view to avoid prolonged inactivity on the part of the hands as well as the opposite fault, into which so many fall, of breaking up the natural flow of their delivery by continual motion.