De civilitate morum puerilium libellus

Fingernails

...with fingernails trimmed, lest any filth should cling to them and you be called ῥυποκόνδυλος a dirty-knuckled person, and previously having voided urine in private, or if the situation demands, having also emptied the bowels. And if it happens that you are dressed too tightly, it is advisable to relax the fastenings somewhat, which would be done with little decorum while reclining. Wiping your hands, cast away at the same time whatever is disagreeable to your mind. For at a banquet, it is not becoming to be sad, nor to sadden anyone. When commanded to consecrate the table, compose your face and hands for religion, looking at the host of the banquet and bending both knees at the name of Jesus. If this duty has been delegated to someone else, listen and respond with equal religion. Yield the honor of the seat to another, and when invited to a more honorable place, excuse yourself courteously; yet if someone endowed with authority commands it often and seriously, obey modestly, so that you do not seem stubborn regarding civility.

Hands

When reclining, have both hands upon the table, not together, nor on the edge. For some indecorously keep one or both in their lap.