They're extracted from the actual maps, so it's actual copies of elements they used—they're all hundreds of years old so in the public domain. I think it's a nice way to keep the work alive in a new format, hence why I name the sets after the engraver/cartographer.

Making brushes is easy. Extracting them from maps can be a bit complex since I do color correction and sizing, and depending on the source material's quality it can be a bit trickier.