Hear me out....

...when bolted onto something that can itself handle 300lbs.

The average unreinforced Prius is good for about 200, if you stick to paved roads anyway.

And yes, the brakes can handle an overall combined payload of about 1000lbs including driver.

 

Will your license plate be visible?

 

It's different with a trailer supporting its own weight on wheels, and a carrier just projecting out back from the hitch.

A common way a hitch is attached on a Prius is by using the shipping hold-down bolt locations in the underbody "frame" rails, a foot or so forward of the bumper. Each "rail" has two bolt locations, a couple inches apart.

So you might be attaching a hitch to those, with a carrier sticking a few feet beyond that, carrying 400 pounds of static load five feet out from the attachment point, which is bolt locations a couple inches (or a sixth of a foot) apart. So multiply the 400 pounds by about 5✕6, or 30, to see the 12,000 foot pounds of torque being put on the mounting location. (Ok, there are two rails, so 6,000 ft lb at each.) Before adding dynamic forces as you bounce down the road, and before some rambunctious kid chasing his buddy through a parking lot takes a running jump off the corner of your carrier for fun.

I had a hitch like that on my Gen 1 and a paid somebody to weld extensions to it that ran a couple feet further forward along the car's rails to where a couple other existing holes conveniently were. Then I worried much less about those torques.

Some hitches might install to the bumper reinforcement mounting locations instead, which sounds like a better plan.

Toyota didn't start offering an official hitch until Gen 4, in Europe. If you look at the installation instructions for that, you take out the bumper reinforcement mounts and slide the hitch's arms forward into the hollow underbody rails, and then bolt it in place. That looks like a pretty good design.

 

And your turn signals, brake lights?

This is my pet peeve...

 

what about one of those small bike trailers?

ace-single-rail-folding-motorcycle-trailer

 

They make the haul much simpler, an average Prius would have no difficulty at all pulling a bike on one of those, even with the cheapest 1-1/4" hitch and no special reinforcements.

But they're a major pain in terms of storage, maintenance and registration.

Now... renting a trailer like that gets you the best of both worlds, but isn't commonly available.