You do know that those are Atlas Stones, and are meant to be lifted onto platforms or over bars, and are not generally used for some quasi Mr. Miagi training, right?
Actually a buddy of mine was bragging that the Royal Marines were doing squats on a swiss ball. I told him that there are some soccer players at the local gym here that stand on them for 5 minutes at a time and then squat and then stand...but I'm not out to be a soccer player or a Royal Marine...