Emily Post, b. 1873, d. 1960. She was born Emily Price, daughter of a wealthy architect and his wife. She was educated at home (homeschooled) and later attended a finishing school in New York. Her society marriage ended in divorce, and she was forced by financial circumstances to write in order to support herself. Her 1922 book on etiquette became a bestseller and provided a comfortable living.

Emily Post’s NY Times obituary
Etiquette in Society, in Business, in Politics, and at Home by Emily Post, published in 1922.

Manners are made up of trivialities of deportment which can be easily learned if one does not happen to know them; manner is personality�the outward manifestation of one�s innate character and attitude toward life…. Etiquette must, if it is to be of more than trifling use, include ethics as well as manners. Certainly what one is, is of far greater importance than what one appears to be.