A windmill built entirely of cloth, with its costing
Tall cloth sails, an eight-piece millstone and a reckoning of 27 3/7 gold ducats
Leonardo designs a mill made entirely of cloth apart from its framework, its sails one cloth-width wide and 25 braccia or more tall so as to catch the greatest quantity of wind, while the sails c d are three cloth-widths wide. He reckons the cloth at 32 widths, costing 6 lire each, amounting to 27 gold ducats and 3/7, with the timber and workmanship costing as much again. The millstone is of eight pieces, and the ritrecine is powerful enough to grind at two millstones in any wind. A margin note reminds him to inspect the fir-poles at the Porta alla Giustizia, and windmill elevations, vertical-axis rotors and a star-shaped rotor plan fill the sheet.
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A mill made entirely of cloth
The mill is all of cloth save the framework; its sails are one cloth-width wide and 25 braccia tall or more, because the taller they are the more wind they catch, while the sails c d are three cloth-widths wide and equally tall. The drawings show the sailed windmill on its stand together with vertical-axis drum rotors and a star-shaped rotor plan.
An eight-piece millstone grinding two palmenti
The millstone is made of eight pieces, and Leonardo notes that the mill is of such power that its ritrecine will grind at two millstones. He adds that it is strong and grinds in any wind.
Reckoning the cost in lire and ducats
The cloth, figured at 4 soldi the braccio, comes to 6 lire each, in all 27 gold ducats and 3/7, and the timber and workmanship amount to as much again. The costing runs continuously across the two blocks beneath the figure.
Cost arithmetic in the margin
The upper-left corner carries the working figures behind the estimate, including 32, 6 and 192 and the conversion to 27 3/7. These reduce the cloth reckoning to the ducat total quoted in the text.
Reminder to inspect the fir-poles
A note to himself reads: look tomorrow morning at the fir-poles at the Porta alla Giustizia, to see whether they are good for this purpose. It ties the design to materials Leonardo means to procure.