"So, my favorite story involving a defacatorium...well, we were doing fieldwork in Ethiopia..."
...and so began one of the most memorable lectures that I have ever experienced. The instructor, Mark Aldenderfer, is an archaeologist with a deservedly strong reputation. The purpose of this lecture was to describe surface collection strategies for archaeological survey, and the story that best illustrated one such method involved a defacatorium - that is, a place where people go to relieve their bowels. So, the sites surface was covered in human feces (that's shit, for those who dislike the technical terms).
See, this defactorium was on top of an archaeological site. Prior to excavation, Aldenderfer and his crew wanted to get an idea of what types of materials they were likely to find while excavating, and also where some of the artifact concentrations were likely to be located - generally, they wanted to know what the site's internal structure was likely to be. This required doing surface reconnaissance, and it was determined that collecting a sample of material from the surface of the site was the way to go.
The collection method that they decided to employ involved taking a hoop, laying it on the ground, and collecting all of the artifacts on the surface within the hoop. Doing this they would hopefully get a solid sample of the site's constituents while also being able to get an idea of what the sub-surface portion of the site looked like.
The instructions given to the field technicians was that they should place the hoops down at pre-determined spots, pick everything off of the ground, and place it into a bag for sorting at the field laboratory.
...and this was when Dr. Aldenderfer learned that you should always be specific with field technicians - when you say "everything" you should clarify by saying "everything archaeological, leave the rest." When the bags were opened back at the lab and poured out onto the sorting tables, it was discovered that not only had the field technicians collected all of the artifacts, they had also collected chunks of feces that were on the surface.
Luckily, when my field techs screw up in a similar fashion, I only end up with pieces of recent trash. There are perks to working in locations where indoor plumbing is the norm.