This U-tube probably formed part of the instrument illustrated in the Saggi di naturali esperienze [Examples of natural experiments] (Florence, 1667) and used to demonstrate the changes in atmospheric pressure. The tube was placed on a base, with the two pipes parallel and divided into degrees. One pipe ended in a trumpet-shaped aperture; the other pipe, in one or more hollow crystal spheres, the last of which was fitted with a long spout to be flame-sealed after the introduction of mercury. When the instrument was delicately moved to the top of a tower, one could observe changes in the level of mercury in the pipes due to the lower atmospheric pressure. The Cimento academicians performed this experiment at the Palazzo Vecchio in September 1657, comparing the degrees on the same barometer at the Piazza della Signoria ground level and at the top of the tower. In the two different situations, they observed noticeable variations in the height of the thin mercury column. This corroborated Blaise Pascal's finding at the summit of the Puy de Dôme in 1648. The academicians reproduced the experiment at Villa Artimino, a property of the Medici.