TBH I kinda forgot the rest of it, since the fact there were three and they had such an unusual theme was the interesting part. Pre-modern history can seem a bit repetitive to me, it's one group of aristocrats trying to knock off another group ad infinitum. I prefer to read about technology, culture and common life, where it's known.

Looks like the first one was proto-protestant rebels, and sparked a religious war. The second was a coup against a Hungarian king who was getting too powerful for the defenestrator's tastes, and featured the defenestration of already dead bodies, 'cause why not.

More people have been thrown from windows in Prague since the third one you were thinking of, but none of them has really caught on as an event. It was sometimes Russian assassins, or course.