One Friday last month I was in the Northern Province of Rwanda for Getaway magazine. Broadly speaking I was in search of gorillas, but at this precise moment I was looking for a hotel. We were on a long back road across a green plain between blue volcanoes, but the Montana Hotel was nowhere to be found. Emmanuel the driver was becoming twitchy. If we carried on much further, we'd find ourselves in Uganda. He didn't want to go to Uganda. I gathered there was some messy business awaiting him in Uganda involving a wife.I examined my brand-new phone with the map application. "Let's take this road to the left," I said."That's not a road," said Emmanuel."The map says it's a road.""I know my country," said Emmanuel. "That's not a road."I looked at the map again. There it was, a solid clear line, an undeniable road. I'm all for rustic local knowledge, but I had a map."Let's take the road," I said.It wouldn't be accurate to call the track we took rutted. It was more like a rut with occasional gestures of track. The blue dusk dropped around us as we bounced and jiggled and lurched."Look," said Emmanuel, pointing through the windscreen with grim satisfaction.He was right. The track had given up any pretence of being anything but hillside. According to my phone map, we were on a smooth, flat expanse of tarred road. It was beautiful and soothing, but even I could see we weren't on the map, we were somewhere stuck in reality."The reality must be wrong," I declared, but in my heart a terrible suspicion grew. Was I in the grips of a mountweazel?Let me explain. In 1975 an edition of the New Columbia Encyclopaedia had on page 1850, in the "M" section, a biographic entry for one Lillian Virginia Mountweazel, a well-regarded mid-20th-century American photographer born in Bangs, Ohio, whose work featured in several solo exhibitions and who published a number of coffee-table photography books, including a study of postboxes of the American mid-West titled Flags Up!, but who died tragically young in an explosion while on assignment for Combustibles magazine.You would probably have to be a student of postbox photography or a subscriber to Combustibles magazine, or perhaps a member of the extensive Mountweazel clan with a particular interest in your lineage and genealogy, to spot instantly that this was an entirely fictitious entry, a tracking signal hidden in plain sight, a dab of invisible ink on a banknote in case it gets stolen.The publishers of encyclopaedias, maps and dictionaries find themselves in a tight spot when it comes to preventing piracy. How does a mapmaker enforce copyright on what is effectively a set of objective facts about the world? How do they copyright a road system? And if you're a dictionary company, how can you prevent some other dictionary company duplicating your extensive and expensive initial research work by simply scooping up your word list? Well, if you're a mapmaker, you include trap streets in your map.A trap street is a fictitious side street (or sometimes a minor geographic feature, like an inlet or a krans or a koppie) that you've invented, whose presence on someone else's map is proof of their pilfering and perfidy. With dictionaries and encyclopaedias, a false entry that operates as a trap street is called a mountweazel, in honour of the eponymous Lillian. I am reliably informed that the Germans have, as Germans do, their own word for a mountweazel, nihilartikel, although I'm not entirely decided if this is an actual word, or if it is, in fact, a mountweazel pretending to be a real word describing a mountweazel.For some people the discovery that the dictionary is a refuge for lies and jokes and lacunae of truth is unsettling, but I like it. Nothing can ever provide a full and complete account of the world, and much of our trouble as humans lies in our inability to grasp that, so I love the thought that even the most serious and authoritative of humanly printed books - legal texts, the Government Gazette, Larousse, the Koran, the Bible - might be studded with jewels of misdirection and error. Ordinarily we have to rely on printing errors and mistranslations for those effects, so the thought of deliberate japes and pranks scattered like mustard seeds through our earnestness delights me like a small child.Or at least it does until I find myself in the lightless Rwandan night, staring dolefully at the stupid map on my stupid screen."Sorry, Emmanuel," I said as he made a juddering u-turn over boulders and through rivers.Emmanuel looked at me in the rear-view mirror. "I know my country," he said...