“A gentleman never looks out of the window.” — Oscar Wilde
“Gentlemen do not take soup at luncheon.” — Lord Curzon
“Gentlemen are never busy — insects and city people are busy.” — Beau Brummel
“A gentleman never sits in the house with his hat/cap on in the presence of ladies for a single moment... People who sit in the house with their hats/caps on are to be suspected of having spent the most of their time in bar rooms, and similar places.” From an American Manual of Etiquette, 1866
I've been terribly guilty of the second and the fourth!