Words which do not satisfy the ear of the hearer weary him or vex
him, and the symptoms of this you will often see in such hearers in
their frequent yawns; you therefore, who speak before men whose good
will you desire, when you see such an excess of fatigue, abridge
your speech, or change your discourse; and if you do otherwise, then
instead of the favour you desire, you will get dislike and
hostility.

And if you would see in what a man takes pleasure, without hearing
him speak, change the subject of your discourse in talking to him,
and when you presently see him intent, without yawning or wrinkling
his brow or other actions of various kinds, you may be certain that
the matter of which you are speaking is such as is agreeable to him
&c.