As someone reputed among certain historians to have given you the epsilon Cauchy startled me by using $\varepsilon$ to denote an infinitely small number in his 1826 text on differential geometry; see page 98 here:
[S]i l'on désigne par $\varepsilon$ un nombre infiniment petit, on aura $$ \frac{\sin\left(\frac{\pi}{2}\pm\varepsilon\right)}{r}= \frac{\sin(\pm\Delta\tau)}{\sqrt{\Delta x^2+\Delta y^2}} $$
Are there other instances of such nonweierstrassian usage by Cauchy?
