It's standard nowadays for the real line to be horizontal (negative numbers on the left, positive numbers on the right) and for $i$ to be above (rather than below) 0 in the complex plane. Were these conventions universally adhered to in the past?
For instance, I don't know how Argand and Wessel and Gauss actually drew the complex plane.
For that matter, did Oresme (who used something resembling Cartesian coordinates) always draw time as going from left to right, and time-varying quantities on a vertical axis?
(This question is also https://mathoverflow.net/questions/286637/variants-in-graphical-presentation-of-real-and-complex-numbers at MathOverflow. I'm new to HSM, so please feel free to correct my tags if others would be more appropriate.)