Four symbols

Here is a diagram involving the four symbols in the graphic lambda-Scale:

– At the left are used drawing conventions from the preview paper “Local and global moves on planary trivalent graphs, lambda calculus and lambda-Scale“.

– At the right are used drawing conventions from “Computing with space…” page 21.

We can pass from a drawing to another by a graphic beta move.

To me, this looks like

$e^{i \pi} = -1$

a formula which involves four symbols too.