> Pi = 3, coincidentally, is the Hebrew Bible's approximation too.

Certainly it's not explicitly spelled out. The example I've heard was the outer diameter and inner circumference of a vessel's circular rim were given. Pi comes out to 3 only if the thickness of the rim of the vessel is zero.

Yes I was over-egging the cake.

It is a large cast bowl in 1 Kings 7:23ff. It's beloved of a certain kind of 'gotcha' internet skeptic "Proof that the bible thinks Pi is 3 !!1! How dumb are teh Christians!".

But the passage itself even mentions the thickness of the bowl, and there's no reason to assume the numbers are anything more than a description of a particular bowl (which inevitably wouldn't have been perfectly circular).

even if the measurements were both outer measurements, the actual value of pi is within the typically assumed error bounds (30/10 < pi but 30.5/9.5 > pi.)

When I took astronomy, anything within an order of magnitude (10) was considered to be the same number. Calculations are very easy when you're only worrying about the number in the exponent.

Feynman was talking to some students, and he used some historical event as an illustration, but he got the date wrong by a few years and they called him on it. He laughed and said "Hey, three decimal places is pretty good for a theoretical physicist!"

In astronomy, you only need to get the order of magnitude right to within an order of magnitude.

"Everything is linear if plotted on a log-log plot and with a fat enough magic marker."

- Mar's Law

There were some exercises in our high school physics textbook which required you to simplify a fraction by assuming pi^2 = g.

Another nice one is that there's pi*10^7 seconds in a year. Which is accurate to three decimal places.

"pi seconds are a nanocentury" is attributed to Adm. Grace Murray Hopper and it's surprisingly useful to know.