Emily Dickinson Lexicon

STEEL-YARD, n. [steel and yard.]

The Roman balance; an instrument for weighing bodies, consisting of a rod or bar marked with notches, designating the number of pounds and ounces, and a weight which is movable along this bar, and which is made to balance the weight of the body by being removed at a proper distance from the fulcrum. The principle of the steelyard is that of the lever; where an equilibrium is produced, when the products of the weights on opposite sides into their respective distances from the fulcrum, are equal to one another. Hence, a less weight is made to indicate a greater, by being removed to a greater distance from the fulcrum.