Here we have a page from the 1999 Scholastic-published book "Dinosaurs to Dodos" by Don Lessem. You'll notice the gigantastic tarantula chasing a giant 6ft long megamillipede of the Silurian.
Read the text: Megarachne is described as a foot across in the body and extrapolated to a span of 8 feet. I couldn't remember reading about any 8 foot spider anywhere, so I went to teh Google and found that 'Megarachne' is an odd eurypterid (sea scorpion) that was originally identified as a spider, and reinterpreted in 2004. http://scienceblogs.com/laelaps/2010/03/megarachne_the_giant_spider_th.php
Now this was from 1999 so the spider thing is forgiveable, but... everything I read about the fossil on the web said that the leg-span was estimated at around 20 inches. INCHES. Where the hell did they get 8 feet from?? Isn't this guy a super scientastic paleoperson?
An amazing example of inaccuracy, and only from 10 years ago. Amazement! Then again, I'm open to any reasonable explanation of this...