it's all in the mind, really
"An Amish man doesn't need to see sexy lingerie to get him excited. He can be aroused by simpler things, like the sight of his wife churning butter or milking a cow."
Of course, it's all in the mind. The Amish alternative to Viagra could well be: "just lie back and think about milking cows and churning butter". Somehow, that doesn't seem quite right.
(If that last link requires a login, this may help)