The human body is a marvelous thing. We go from a single cell to a complex fleshy machine that can write operas, lift Camaros and…fit five pounds of heroin in our guts.

Drug muling, Popular Science explains, is just putting a twist on something your body does really well, anyway: "Your entire body is designed to help take things from your mouth and pass them out your anus, with some time in between. When smuggling, that's exactly what you want."

So how much contraband can the average person cram into their digestive tract, and how long can they keep it there?

"As for capacity, well, nobody knows, really. Typically a packer or mule will carry about 50-100 of these packets, but folks have been caught carrying in excess of 200--as much as five pounds, concealed in the gastrointestinal tract.

...When swallowing packets of drugs, the length of time they stay within the body is mostly up to the literal intestinal fortitude of the packer. Generally it'll take about a day or two to pass through the system, but if the packer is desperate, times of as long as five days (five agonizing days) have been reported."

Getting the merchandise into your body from the other direction is a little trickier. You're fighting against the natural direction your ass and intestines want to push things, and there's only so far you can shove before you risk poking a hole in something important. Any idiot can swallow a balloon full of coke, but keistering is the realm of professionals.

The key to stuffing, as in so many things, is practice. Accomplished rectal stuffers, many of whom can be found in our prison system, work both to expand their rectal capacity and, at least as importantly, to train their bodies to suppress the urge to defecate.

Practice makes perfect. Also, stretchy rectums, which, of course, medicine has a name for: megarectums. For folks who've done this a lot, the sky is the limit when it comes to using a butt as a suitcase. If you haven't put in the work to mega-size your rectum, though, then you'll be lucky to fit half a kilo in there, amateur. [Popular Science]