Institutio Oratoria

He will also insist that the speaker faces his audience, that the lips are not distorted nor the jaws parted to a grin, that the face is not thrown back, nor the eyes fixed on the ground, nor the neck slanted to left or right. For there are a variety of faults of facial expression. I have seen many, who raised their brows whenever the voice was called upon for an effort,

others who wore a perpetual frown, and yet others who could not keep their eyebrows level, but raised one towards the top of the head and depressed the other till it almost closed the eye.