According to Arnol'd himself (we are not worthy, we are not worthy...) Poincare had published a paper in the proceedings of the French Philosophical Society in the late nineteenth century sometime, on electromagnetism, but since the paper was intended for philosophers, there were no equations in it, except one, on the last page, which was $E = m c^2$ -- apparently this was too cool to resist. Apparently, Poincare was, in fact, the referee of Einstein's special relativity paper, around a decade later, and recommended it for acceptance, and when people asked him why, given that he had known the stuff for a while, he responded that this seems to be a bright young guy, and such should be encouraged. I am not sure where this is written down (I heard it from Arnold in person). Perhaps someone here knows the actual facts.