The Book of Household Management by Mrs. Beeton

some of your friends, to persons living in the neighbourhood to which you have just come. In this case inclose the letter of introduction in an envelope with your card. Then, if the person, to whom it is addressed, calls in the course of a few days, the visit should be returned by you within the week, if possible. Any breach of etiquette, in this respect, will not readily be excused. In the event of your being invited to dinner under the above circumstances, nothing but necessity should prevent you from accepting the invitation. If, however, there is some distinct reason why you cannot accept, let it be stated frankly and plainly, for politeness and truthfulness should be ever allied. An opportunity should, also, be taken to call in the course of a day or two, in order to politely express your regret and disappointment at not having been able to avail yourself of their kindness.