Truss

A bound bundle of hay or straw, with three distinct weights fixed in law: 60 pounds for new hay, 56 for old, and 36 for straw.

The three weights exist because hay loses moisture as it cures. New hay, cut in the current season, still holds water; old hay from the previous season has dried out. Selling new hay at the old weight therefore meant selling water at the price of fodder, and successive Hay and Straw Acts fixed all three figures precisely to stop it. Thirty-six trusses made a load, and the trade was substantial: London ran on horses, and every cab, omnibus and dray in the city needed feeding and bedding. The Haymarket takes its name from it, and the markets at Smithfield and Whitechapel were considerable commercial institutions. The Acts were repealed only in the twentieth century, by which time the horses had gone and the fraud with them.