If you're ever in the Netherlands I can recommend a visit to the Zaanse Schans where they have a mill[1] from the days when pigments were ground with windpower. You can see the colors and you'll have a better understanding of why Royal Blue[2] was Royal (because it was incredibly expensive to make a lasting blue pigment).
Fascinating stuff.
I imagine it would be a rabbit hole, but rabbit holes can be a lot of fun. I will have to work with the poor-man pigments though. No ultra expensive gemstone grinding for me :-).
Good quality pestles can be found on flea markets, people hardly ever use them now so they don't appreciate what they've got.
What I find fascinating about Löffelholz's drawings is how alive they look. I guess he used a pencil for sketching, then ink for the outlines, washes for coloring and shadows. Then bright white paint for highlights.