What really weighs what -- and where?
Remember your multiplication tables.
Aerarium/Weights (a.d. XIV Kal. Iun)
The Acta and scrolls will tell of a break-in at the Aerarium and the possibility that the weights were tampered with. Go to the alley on the east side of Castor and Pollux (not the one where you found Gordian's strongbox in January, but the other side). Go through the Aerarium doors on the right and go around to the back of the room (right, ahead, left, ahead, left, left). You'll see a scale, a lever, some numbered weights, and a funnel marked "XXXV" (35).
Hang the weights in this order: I, II, V, IV. Pull the lever so that sand flows into the scale pan, until the scale is even (if you go too far, just keep letting the sand flow until the pan dumps itself, then pull the lever to start again). Remove the pan and pour the sand into the funnel. A niche above the funnel opens, revealing a stylus, a weight, and a scroll. (Clue: in one of the scrolls or Acta, there is a reference to the weights being tampered with. IV is debased by 1/4; and the hooks increase in multiples, i.e., 1st=x1, 2nd=x2, 3rd=x3, 4th=x4. Thus, the 1 1b. weight on the first hook is 1 lb., the 2 lb. weight on the second hook is 4 lbs., the 5 lb. weight on the third hook is 15 lbs., and the debased 4 lb. weight on the fourth hook is 15 lbs. Total: 35 lbs.; you have to put 35 lbs. of sand in the funnel to open the niche.)