Children (until 1920)
Over time, establishments like the US Postal Service have been able to find loopholes and iron them out. In most cases, it just takes someone to exploit it for that to happen. That’s what happened throughout the early 20th century, when the rule was that they would ship anything under 11 pounds. Taking advantage of that ‘anything’ rule, the Beague family paid a small amount for stamps and insurance on their baby son and shipped him off to their grandmother’s house! Luckily, he wasn’t to be packed away in the belly of a plane and was instead just carried by the mailman to that house only a mile away.
This was surprisingly common in the US, as the cost to send them was often cheaper than just buying them a train ticket. It took several more human deliveries, and many more perturbed mailmen, for an anti-child shipping law to come into effect just a few years later.