I had the pleasure of having to do this a few months back.
Biggest issue I faced was how to get it from, ah, source to destination. You can’t do it directly, surely? There’s no way my nipsy could squeeze out something that narrow without fitting some sort of icing bag attachment, or a funnel arrangement or something.
The alternative seemed to be to go as Thomas Crapper intended, them fish out lumps of Richard from the bowl. But I was concerned that watery, bleachy tagnuts would be sub-optimal for analysis purposes.
I ended up hacking off the bottom of a 2L Coke bottle to use as an intermediate hopper. Now let me tell you, you might think you know where the hole in your arse is, but all bets are off when you’re sitting on the throne with your arm between your legs, brandishing around your nether regions a sawn-off plastic bottle with an edge that could be used for really niche shaving, trying desperately not to lay a cable along your wrist. One false move and you’re going to end up with wounds that are going to take a considerable amount of explaining.
Once you’ve got a deposit, and you obviously don’t need much (though crimping off mid-poo is trickier than you think), you’ve got an immediate issue of now having a steaming receptacle of doom in your hand whilst you’re still mid-thrutch and quoting Magnus Magnusson. So you’ve got a bit of a quandary as to which to take care of first. If you’ve luckily managed to restrict your output to just the inside of the pot, you can at least put it down for a minute whilst you sit and think.
Filling the vial is, unsurprisingly, tricky. When the human body’s excretion system was put together, the ability to chop up a soggy Morph with an ice cream spoon wasn’t high on the list of design criteria. Nonetheless, with a bit of patience it is possible to get a couple of scoops in the damn thing (and all over your hands and legs). You particularly need to be aware that the stem of the scoop is quite springy, and has a tendency to ‘ping’ its contents about the place. Fortunately, most modern bathrooms have easily wiped tiles.
Once you’ve got your vile vial, you’ve still got the hitherto unconsidered problem of what to do with your impromptu catcher’s mitt. To be honest, if you’ve come this far then I’ll leave this as an exercise for the reader. You probably don’t want to stick it in the bathroom bin though.