Mistresspiece

This Herb is Venus’s Miſtreſs[-]piece, and is as gallant and univerſal Medicine for all Diſeaſes coming of Heat, whereſoever they be, or in what Part of the Body ſoever they be, as the Sun ſhines upon; […]

Source: wiktionary

I am not about to wax eloquent or magniloquent—a very different style of thing—on the subject of galleries of art. For in that case I should be obliged to say much of the master-pieces and mistress-pieces of all the collections of all the countries on the face of the earth.

Source: wiktionary

He might have drawn her picture, standing, with arms akimbo, in the act of addressing the House, and demanding, in stentorian tones, the rights of those whose interests she represented; her speech a mistress'''piece of powerful rhetoric, its peroration a threat!

Source: wiktionary

I have lately been reading novels for grown-ups instead of for boys. They mostly bore me. Too much petticoats in them, Deadwood! The puffs about them read like this: “Deals with the relations of man and wife and the struggle between the sexes that characterizes our day.” Or they are about “the feminine lure and modern passion.” Modern passion! What do you know? as they say in the Black Hills. Bored stiff with these masterpieces and mistresspieces I wrote this book, partly for money to pay for the feed of my wife, my horses, myself, and partly for fun.

Source: wiktionary