I learned this back in the early 2000's because I moved to a new city, didn't have a cellphone, and was waiting for my landline and internet to be hooked up. So I literally knew no one and had no contact with the outside world. Then, seriously, I happened to find a set of juggling balls in the back of the closet of the room I was renting—the previous tenant must have forgotten them there.

With literally nothing else to do, I taught myself to juggle. Took me longer than an hour, but not all that much longer. (Started with one ball tossing back and forth, then two, before moving to three.)

That rings true, I spent a weekend in the 90s to teach myself. I taught a bunch of people to juggle since - usually with an instructor an hour to reach something like juggling is achievable.

For most people this will take more than an hour to master, but once you get to around five tosses and catches you've figured out the pattern and the rest is just practice.