I'll freely admit that my closest brush with carpentry is IKEA products, so I'll take your word that oak might not be appropriate. In my defence, I'll say that I googled a bit to try and figure out what wood to pick, and I found somewhere that mine carts are made from oak, thus why I picked that material.
But even if I drop the weight by 33%, and then halve it to represent a weak box (non-reinforced, even though that's not what the comic shows), we are still at almost 300 pounds for the box (278, to be precise). MitD is unlikely to weight 22 pounds, unless he is buoyant.
This makes the hardest kind of sense. Picture that box in real life, i.e. a wooden cell taller than you, broader than a door and twice as long. There is no way an average human is going to be able to lift it even empty.
Grey Wolf