Or I would be overjoyed to know even the earliest known use of the common symbols for +, -, the multiplication symbol, and the division symbol (the line between two dots, which I don’t know how to render here).
The multiplication symbol’s interesting, too… when did all those alternatives to that stylized x spring up? If it’s as long ago as I think it is (since we’ve been using x to signify an unknown), why are we still stuck with it today? And did the x symbol pre-date the letter?