I remember seeing sketches of catapults and military inventions, which Leonardo da Vinci put together as marketing material and a sales pitch (I believe to the

I remember seeing sketches of catapults and military inventions, which Leonardo da Vinci put together as marketing material and a sales pitch (I believe to the lord of Milan). Like, "I can create all sorts of machines both for the protection of a city and for siege." It struck me how being an entrepreneur - learning to swim in the realities of the market - was (and is) an essential part of being an artist.