Some traditions say, based on the Gemmorah in Taanis 9a (also מדרש רבה נשא י' ו', זוהר פנחס רכ"א א, and more):
"ליכא מידי דלא רמיזא באורייתא" (Is there anything that is written in the Writings that is not alluded to in the Torah at all?)
that everything can be derived from the written Torah (the Pentateuch of 304,805 letters, and Gr"a adds from Parashat Bereshis alone etc). Many tried (and succeeded) to find certain integers, such as numbers and dates.
In what way can the irrational and infinite number Pi be derived from the written Torah?
(to clarify, the question is not about approximation of Pi, it is about the possibility to derive an irrational number from a list of letters)