I kind of went the other way. I skipped out on my undergrad classical mechanics class and did the graduate course, taught by a guy from the Landau school, out of volume 1 of Landau & Lifshitz. So in the summer after my 3rd year I spent some quality time with Newton's Principia and then most of the rest of the summer staring off into space as I hooked up everything between the two systems again.

Man, that was a great summer.