Cold Water in Overheated engine=cracked block. Is there proof?

I was have having a discussion about this the other day.

Do you any of you know of an actual incident of someone putting cold water into an engine that is overheated and caused a cracked block?

We are talking old iron block cars here.

My stance was that it seems possible, but I won't believe it as fact until I find actual proof.

My hesitations are:
-can cold water be introduced quickly enough in a large enough quantity
-how did you get the radiator cap off if it was so hot?
-how hot does the engine have to be/how cold does the water have to be
-how did you get the cold water from its location to your overheated car fast enough for either the water to be cold enough or the engine to be hot enough
-how do you know that the cold water was the cause and not the fact that you overheated your engine severely

Again, the theory makes since. Is there an actual occurrence that you know of?