In the 1800's and early 1900's, the practice of "calling" upon or visiting relatives and friends was a refined affair: people used calling cards as as a mean of introducing themselves, as notes of thanks, or even as a polite brush off!
Calling card, which has since fallen out of favor, is making a big comeback. In their timely article, Brett and Kate McKay of The Art of Manliness explain the ins-and-outs of calling cards.
Here's an interesting fact about calling cards I've just learned:
Generally upon a gentleman’s initial visit to a home, he would simply leave a card and then depart. If the new acquaintance wished to formally visit with him, he or she would send a card in return. If no card was sent, or the return card was sent in an envelope, this signaled that the new acquaintance did not wish for a personal visit to occur. This signal (the card in an envelope) could indeed be sent after any visit in which the visited party no longer wished to be called upon by this particular person. It was basically the well-mannered brush off.
Link - Thanks Muhammad!
Previously on Neatorama: Here's My Calling-Emailing-AIMing-Twittering Card