Projectile motion, a jibe at doctors, and Salai's expenses
How a moving body loses power to the air, with a 1504 household account in another hand
Folio 147v opens with a sardonic remark urging one to get the diagnosis and remedy 'from the Saint and the other', for men are chosen as physicians of diseases they do not know, then turns to the physics of moving bodies. Leonardo holds that a projectile keeps its straight transversal motion only while the power imparted by its mover lasts, and works a numerical example in which a power of 10 is worn away by a medium resisting by 1 until the motion ends in nine degrees. Folio 148r bears, in another hand thought to be Salai's, a dated household account begun on 25 May 1504 after receiving 15 gold ducats from Leonardo, itemising bread, wine, meat, a barber, a ring's resetting and other daily costs. The leaves carry further writing and small diagrams not all transcribed here.
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A projectile's power consumed by the resisting air
The motion of a movable follows the line of its mover's motion for as long as it keeps the whole power given at separation. Leonardo sets that power at 10 against a medium resisting uniformly by 1 over ten degrees of length, so the power falls degree by degree until the motion is spent in nine degrees.
Salai's dated account of household expenses, 1504
Begun on the morning of San Zanobi, 25 May 1504, after receiving 15 gold ducats from Leonardo di ser Piero da Vinci, the list records daily outlays in soldi and denari — to Mona Margarita, resetting a ring, cloth, a barber, eggs, wine, bread, meat, fruit, mushrooms and candles — across Saturday, Sunday and Monday.
A jibe at physicians treating unknown diseases
The folio opens by telling the reader to get the definition and remedy of the case from 'the Saint and the other', adding that one will see what men are chosen as doctors of illnesses they themselves do not understand.