Last package of the da... Yo wtf?!?

Not to be a killjoy but your basic mailman has a pretty low weight limit on the parcels they take.

But sometimes I have mildly inconveniencing experiences with the postal service in my extremely rural town that require me to navigate my extremely rural town's nearly non-existent public services so we should absolutely surrender complete control to Amazon

But do you fit into that box? 🤔

I'll go one better.
A (non-spinning uncharged) black hole with diameter 1+5/8th inches (so it fits in the box) has a mass of about 2.3 earths.

(Near as I can tell QGP filling the whole box is around a ten billionth of that.)

Of course the box would Very quickly no longer be outside the black hole. QGP would also cause the box to no longer be a container in short order. To put it mildly.

This is the case for most "Dumb laws": there's an outlier that becomes kinda silly, but it's not really worth the effort to change.

I saw one "It's illegal to hunt Blue Whales in Idaho". Because it's illegal to hunt endangered species in Idaho, and Blue Whales are endangered, not because legislators were super concerned about saving Idaho's whale population.

If mailing 70 lbs of unstable particles that can't exist outside of a lab is wrong, I don't wanna be right.

No you mean theoretical. As neutronium is a theoretical substance. To our knowledge there's no way to find it outside of neuron stars. It is therefore physically impossible, within our current state of knowledge.

It's highly unlikely, bordering on theoretically impossible to assume that mankind will be able to synthesize enough to fill a cardboard box with. Then the practical side says even if that was possible, there would probably no way a cardboard box could contain that (and a plethora of other practical impossibilities).

Such devices exist, namely stars. Neutron stars are theorized to have neutronium at their core, essentially a soup of neutrons so densely packed that nothing else fits between them - in order words, the densest theoretical material (osmium is the densest material found on Earth).

I believe that would be some form of fusion

Good news, it's 20-30 years away!

The surface area of the box is about 135 inches. If this surface area were spread over a sphere, it would have a diameter of about 6.5 inches and a volume of nearly 150 cubic inches (nearly twice the volume of the uninflated box!). 150 cubic inches of osmium weighs about 120lbs.

So, indeed you could exceed the weight limit of the box by ballooning it out and filling it with something that's at least 7/12ths as dense as osmium (or a little more dense than lead).