I've heard it was, but I can't find anything concrete. Perhaps someone could clear it up?
Not as far as that, although up until the mid-18th century, the Don and Volga rivers were usually considered the Europe/Asia boundary line rather than the Urals. (Christendom Destroyed by Mark Greengrass, among others, mentions that). Catherine the Great's Russia was the entity that tried to claim the Urals and Caucasus as Europe's boundaries as a way of making more of Russia seem European.
Wikipedia has a nice map (this is not my source, just an illustrative visual aid)
B-D would have been the common definition of Europe's boundaries before the 18th century.
