De civilitate morum puerilium libellus

The arms.

To twist both arms behind the back has the appearance of both laziness and theft: nor is it much more decent to stand or sit with one hand placed upon the hips, which however seems elegant and soldierly to some. But that which has pleased fools is not immediately honest; rather, it is what is consistent with nature and reason. The rest will be said when we arrive at conversation and dining.

Modesty to be preserved.

To uncover the members to which nature has added shame without necessity should be far from a liberal disposition. Indeed, where necessity compels one to this, even that must be done with decent modesty, even if no witness is present. For angels are never absent, to whom the companion of modesty, which is shame, is most pleasing in boys. Those things whose sight it is modest to hide from one's own eyes, one should much less offer to the view of another.