Milo, the correct formulation is that math historians reading and studying the Rhind Mathematical Papyrus found one single implicit value of pi, namely 256/81. I discovered many more pi values in the RMP, and they all have one thing in common: they are easily generated with the algorithm of 'false additions' ...
Pi is less than 4 but a little bigger than 3. So begin with 4/1 and add repeatedly 3/1 in the way that was forbidden in school:
By measuring out circles you may find that pi is slightly smaller than 19/6. This allows another sequence starting with 3 in the form of 9/3:
9/3 (plus 19/6) 28/9 47/15 66/21 ... 256/81
There you are with the value 256/81. In the same sequence you find the value 66/21 that equals 22/7, and 22/7 is also found in the first very simple sequence. Pi is more than 3 and slightly less than 22/7. If you know this you can go for the best number sequence of false additions for pi:
This sequence contains a lot of pi values for which I found indirect evidence in the RMP. Using a lot of values around the elusive exact value has a big advantage: you can choose the value that comes handy in the context of a given calculation. The accuracy achieved by this concept of irrational numbers was sufficient for all practical and scientific purposes of the ancient Egyptians.