I’ve started reading Charles C. Mann’s book 1491. I’m really just a few pages into it, but so far it’s quite well-written. I came across a mention of something that surprised me: in discussing the Olmecs and their accomplishments, Mann mentions that the idea of “0” (zero) as a number didn’t reach Europe until the twelfth century. I knew that. But he also added that the idea of the zero was opposed, and the number banned, by various authorities. I poked around a bit on the web, and sure enough found this link where Mann goes into detail about the medieval reaction to zero, and his sources for the information. Worth a look!