The Organum Mathematicum is a fabulous-looking thing:
vps280516.ovh.net/divulgamat15/i…
A box of sticks which form tables to help with mathematical calculations, sort of like Napier rods, but for artillery and music?! Of course this oddity is a product of Athanasius Kircher!

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.

Use $ and $ for inline LaTeX, and $ and $ for display mode.