Explanation: Studying ancient history is like playing Minesweeper, but half the time the numbers don't appear, and if they do, they're wrong, and you aren't even told if you click on a mine at all!
Historians really have no room to be picky about their sources, but this is a reminder not to believe everything some old dude wrote on paper thousands of years ago.
The first image references Book VI of Caesar's Commentarii De Bello Gallico, where he talks about the Germanic tribes. We know he's full of shit because Tacitus (depicted in the second image) gives a wholly different account of the Germanic tribes in his Germania. Although one should be wary of him too, as he never went to Germany in person, and most of his book probably relies on second-hand sources (some speculate Pliny the Elder, considering that some of the information he gives is outdated by the time the book hit the press).
TL;DR: I wish I could travel back in time and punch these guys in the face.