De civilitate morum puerilium libellus

Urine.

To hold back urine is harmful to health; to discharge it in secret is modest.
Flatulence.

There are those who instruct that a boy should restrain the wind of the belly by clenching the buttocks. But it is not civil, while you are studying to appear urban, to invite disease. If it is permitted to withdraw, let him do it alone. If not, according to the most ancient Proverb, let him disguise the sound with a cough. Otherwise, why do they not by the same logic instruct him not to defecate, since it is more dangerous to hold back wind than to tighten the bowels?
How one should sit.

To sit with knees spread, or to stand with legs straddled or twisted, is the way of Thrasos braggarts. When sitting, let the knees come together; when standing, the feet, or at least let them be moderately spread. Some sit with this gesture, that they hang one leg over the other knee: some stand with legs crossed, of which the one is the way of the anxious, the other of the inept. To sit with the right foot placed upon the left thigh is the custom of ancient kings, but it is disapproved. Among the Italians, some, for the sake of honor, press one foot against the other and stand almost on a single leg in the manner of storks, which whether for boys...