It turns out that cats have been licking their butts since (basically) the beginning of time — and humans have always watched them, like big ol' weirdos.
A collection of images from early illuminated manuscripts, dating back to the middle ages, is featured on the Tumblr Discarding Images. Every artist rendering features a cat caught in the act of self-cleaning.
[seealso slug="watching-cat-videos"]
Because the Internet didn't exist during the Medieval days, so this is what people had to do to fill the absence of cat videos.
Here's a sampling of some of the more, um, artistic images: