The Queen is usually reckoned equal, in average situations, to two Rooks and a Pawn, but towards the end of a game she is hardly so valuable as two Rooks.
Howard Staunton (1873). “The Chess-player's Handbook: A Popular and Scientific Introduction to the Game of Chess, Exemplified in Games Actually Played by the Greatest Masters, and Illustrated by Numerous Diagrams of Original and Remarkable Positions”, p.34
