My favorite is of Pi being 3.0:

  1 Kings 7:23
  And he made the molten sea of ten cubits from brim to brim, round in compass, and the height thereof was five cubits; and a line of thirty cubits did compass it round about.

Although in fairness, 1) if you round both the diameter and the circumference to the nearest cubit, it can just about work (the numbers are rather narrowly constrained to 9.66 and 30.34 cubits), 2) the nearest multiple of 5 or 10 cubits might have been considered sufficiently precise for a rough description, and 3) the bowl was "a handbreadth" thick, and if we assume that they measured "brim-to-brim" on the inside and "compass it round about" on the outside, and that a cubit is 18 inches and a handbreadth 4, Pi comes out almost exactly right.