Sixteen sockets and four weights of every gauge: 2, 5, 9 and 14 grains. Each row and each column must hold all four gauges, one of each.
The brass bars give the sum of the two sockets they span. Pick a weight, then click a socket.
A marble slab with sixteen sockets and a set of lead weights. The ordinance demands that no gauge be repeated in the same row or the same column, and four brass bars mark what certain pairs of sockets must add up to. That is enough: there is no more than one way to lay them out.
—