I don't want to rub it in too much, but the little monster in the box here (puppy Hermes on the night we brought him home) was already house broken -and he was exactly 8 weeks and 1 day. OK, he did have a few accidents over the next couple of months since young dogs are simply incapable of holding it that long but he knew the proper place to go, outside.
My wife actually thought this box would hold him. We took the pic a minute or two after putting him in and he was out seconds after it was snapped. One effortless leap.