I've known that Curtis and others few gliders before adding power, but I'd never heard the above story. That's pretty cool.
As things are, I live 7 miles south of Curtis's original base of operations in Hammondsport, NY. There's a small park at the beach where he first flew his (first ever) sea planes.
I think that I have actually walked the hill from which Curtis and others first flew gliders. But I'm not sure where the cliff is that this fellow is referring to. It shouldn't be hard to spot it from the valley. Perhaps I can get some pictures.
The lake mentioned would, of course, be Keuka Lake.