It seems like many years ago now, but it isn't, really. I was asked to leave my mark on his life with a pithy statement that would somehow contain my very essence for him to remember me by. I wished I had more time to think about it, but I had to come up with something on the spot. I could see that my reputation preceded me, for he helped me along by suggesting I write down my favourite equation. Delighted at that brilliant idea, I wrote in my neatest script the equation, e^iπ = 1. It took me a whole day to realize that I had got it wrong, but instead of being distressed, I merely smiled and thought it quite funny. And, in some sense, perhaps a more fitting legacy.