Ancient Egyptians were a crafty lot, what with those pyramids and that cool dance and mummies and all. It's no surprise then that they were some of the first people to cook up a method of birth control that actually worked. They had figured out that you could stop the pregnancy if you had some kind of, uh, blockage there.
Still, these were ancient times and there was an unspoken agreement that everything they did had to be horrible in some way. Thus, they made their sperm barriers out of honey and crocodile shit. Seriously, look it up. We wouldn't lie to you.
Who exactly was the first to try this, and what their logic was, is lost to history. We know one thing though: When they finally invent a time machine, the first thing we're doing is going back to find out.