Memoranda for Milan, with geometric figures after Apollonius
A list of books, people and measurements to pursue in Milan, beside a fragment of conic-section diagrams.
The larger sheet is one of Leonardo's celebrated memoranda: a running list of things to obtain, measure and ask about in Milan, naming friends and masters (messer Fazio, the friars of Brera, maestro Antonio, Benedetto Portinari) and books to track down (Witelo in the Pavia library, Aristotle's Meteora in the vernacular). He reminds himself to measure the city, the Corte Vecchia, the Castle, and the canals with their locks and boats. A separate lower fragment carries five small geometric figures — a circle, a quadrant and three triangles — with a note that they come from near the end of Apollonius' treatise on cones (De piramidibus). The tiny hand is faded but the transcription supplies the reading in full.
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A memorandum of things to obtain, measure and ask in Milan
Leonardo sets himself a program of enquiry: to have messer Fazio show him about proportion, the friar of Brera explain De ponderibus, and maestro Antonio tell how bombards and bastions are placed by day or by night. He notes books to find, from Witelo on mathematics in the Pavia library to Aristotle's Meteora in the vernacular, and measurements to take of Milan, the Corte Vecchia and the Castle. He also records lending certain 'knots' (designs) to Fra Filippo of Brera.
Proportion sought from Fazio, Alchino and the abacus master
Among the intellectual errands are questions of ratio and measure: to have the abacus master show him how to square a triangle, and to obtain 'the proportions of Alchino with the observations of Marliano,' which messer Fazio holds. He also chases down the measurement of the sun promised by maestro Giovanni the Frenchman.
Canals, locks and masters of water
Leonardo means to measure the canal, its locks and supports and the larger boats, together with the cost, and to find a master of waters who can tell him the embankments and their price — an embankment, a lock, a canal and a mill in the Lombard manner. He records that a nephew of Gian Angelo the painter owns a book of waters, and that Pagolino the stonecutter, called Assiolo, is a good master of waters.
Geometric figures after Apollonius' De piramidibus
The lower fragment carries five small figures: a circle described as a mirror, a quadrant taken from the top of a section, and three triangles. A closing note states that these figures are found toward the end of the principles of the learned Apollonius, On the Cones (De piramidibus).