To do list

Leonardo Da Vinci's to do list from 1490.

[Calculate] the measurement of Milan and Suburbs

[Find] a book that treats of Milan and its churches, which is to be had at the stationer’s on the way to Cordusio

[Discover] the measurement of Corte Vecchio (the courtyard in the duke’s palace).

[Discover] the measurement of the castello (the duke’s palace itself)

Get the master of arithmetic to show you how to square a triangle.

Get Messer Fazio (a professor of medicine and law in Pavia) to show you about proportion.

Get the Brera Friar (at the Benedictine Monastery to Milan) to show you De Ponderibus (a medieval text on mechanics)

[Talk to] Giannino, the Bombardier, re. the means by which the tower of Ferrara is walled without loopholes (no one really knows what Da Vinci meant by this)

Ask Benedetto Potinari (A Florentine Merchant) by what means they go on ice in Flanders

Draw Milan

Ask Maestro Antonio how mortars are positioned on bastions by day or night.

[Examine] the Crossbow of Mastro Giannetto

Find a master of hydraulics and get him to tell you how to repair a lock, canal and mill in the Lombard manner

[Ask about] the measurement of the sun promised me by Maestro Giovanni Francese

Try to get Vitolone (the medieval author of a text on optics), which is in the Library at Pavia, which deals with the mathematic.

My personal favourite is "Examine the crossbow of Mastro Giannetto", either a forensic mechanical and scientific process or some kind of weird euphemism. Just imagine what he'd have made of a smartphone.