Various, Notes and Queries, Number 219, January 7…
“ When a paper figure, bent over a straight line in it, has the two parts perfectly fitting on each other, the figure is symmetrical about that straight line, which may be called an axis of symmetry. Thus every diameter of a circle is an axis of symmetry: every regular oval has two axes of symmetry at right angles to each other: every regular polygon of an odd number of sides has an axis joining each corner to the middle of the opposite sides: every regular polygon of an even number of sides has axes joining opposite corners, and axes joining the middles of opposite sides. ”
