He claimed if we look at how the original numbers looked, and placing a dot on each angle, you can see how each symbol has the corresponding number of angles:
While this is interesting, I will have to file it under "apocryphal". First, the 5 has a tail and the 7 has a "base" (I conceded that people use a hash on it in many parts of the world). I also find it hard to believe that a writer of 9 had to draw an octagon (the reply being that is one of the many reasons the digits were simplified over time).A quick web search didn't find any corroborating data, but I didn't spend a lot of time looking. It's interesting, if true, and even if it isn't true, it makes a good story to tell at a bar on a cocktail napkin.