The first time we set him on his stomach on the sofa during dinner and looked up moments later to find him lying peacefully on his back. But I couldn't believe it, so I put him back on his stomach and watched him and a minute later - over again. The third time, we videotaped it. Sadly, by this point he was pretty mad that we kept putting him back on his stomach when he clearly wanted to be on his back, so he's crying in this video. After this, we let him rest on his back - he deserves it.
For those of you not up on their baby development facts, most babies learn to roll over between four and six months. Beatrice did so just shy of three months. Doing it at two weeks - I have never heard of anything like that. In fact, my friend Joanne said that in medical school they were taught that if someone brings a baby into the hospital under 3-4 months old and claims they were injured when they rolled over and fell off something, they should consider that person to be lying, because it's not possible for a baby that young to roll over.
So there you go! Arthur is apparently incredibly strong. He also gained 11 ounces of body weight in six days, so we may have a superhero on our hands.