Considering the density of neutronium, a 70 lb piece would be about the size of a dust mote, if not much smaller. Good luck getting a standard box to hold something that small and dense.
The joke here is that neutronium might be the only substance dense enough to actually weigh 70lbs and still be able to fit into a flat rate box, which has set dimensions and a limit of 70lbs.
Considering the density of neutronium, a 70 lb piece would be about the size of a dust mote, if not much smaller. Good luck getting a standard box to hold something that small and dense.
The joke here is that neutronium might be the only substance dense enough to actually weigh 70lbs and still be able to fit into a flat rate box, which has set dimensions and a limit of 70lbs.