Reads like an introvert's dream:

> The essential convention was that a first person would not expect to see a second person in the second's own home (unless invited or introduced) without having first left his visiting card at the second's home. Upon leaving the card, the first would not expect to be admitted initially but instead might receive a card at his own home in response from the second. This would serve as a signal that a personal visit and meeting at home would be welcome. On the other hand, if no card was forthcoming, or if a card was sent in an envelope, a personal visit was thereby discouraged.

and also:

> Sample lady's visiting card, specifying an "At Home" day

> The "At Home" day was a social custom in Victorian Britain, where women of gentle status would receive visitors on a specific day of the week.