It's funny to think that, as far as these sailors knew, the passage to India could be right on the other side of that waterfall. Or, they could be barely 50 miles inland of a continent over 2000 miles wide. It's what outgoing Pentagon Poet Laurate Donald Rumsfeld would have referred to as a "known unkown."
Happy Birthday to my Grampa, Carl. On the off chance there's an afterlife, here's hoping you're playing bridge with Abraham Lincoln, or drinking scotch with Jesus. And that you have have internet access.