George Washington's Rules of Civility Traced to their Sources and Restored by Moncure D. Conway
Chapter ii. 4. Ne faites pas voir a vostre compagnon, ce qui luy
pourroit faire mal au coeur.
Show nothing to your companion that may grieve him.
4th. In the Presence of Others sing not to yourself with a humming Noise, nor Drum, with your Fingers or Feet.