De civilitate morum puerilium libellus

...make things more decent: what is vicious, if they do not remove it, they certainly hide and diminish. It is indecorous to look at anyone with one eye closed. For what else is this than to blind oneself? Let us leave that gesture to tuna-fish and smiths.

Care of the eyebrows.

Let the eyebrows be relaxed, not drawn together, which is a sign of grimness; not raised on high, which is a sign of arrogance; not depressed into the eyes, which is a sign of those thinking evil.

What is fitting for the forehead.

Likewise, the forehead should be cheerful and smoothed out, showing a mind well-conscious of itself and a liberal disposition, not contracted into wrinkles, which is a sign of old age; not movable, which is a sign of hedgehogs; not grim, which is a sign of bulls.

What is fitting for the nostrils.

From the nostrils, let there be an absence of the purulence of mucus, which is a sign of the sordid. That vice was also attributed as a reproach to Socrates the philosopher. To wipe one's nose with a cap or garment is rustic: with the arm or elbow is for fishmongers: nor is it much more civil to do it with the hand, if you soon smear the phlegm on your clothing.

Handkerchiefs.

It is decorous to catch the waste of the nostrils with a small cloth, and that while turning the body away for a moment, if any more honorable persons are present. If one drops anything onto the ground...