It was not proven, it was observed, or recognized.
Sorry, my mistake. Pi is the ratio of the circumference of any circle to the diameter of that circle. It is 3.14
The importance of pi has been recognized for at least 4,000 years. A History of Pi notes that by 2000 B.C., "the Babylonians and the Egyptians (at least) were aware of the existence and significance of the constant π," recognizing that every circle has the same ratio of circumference to diameter. Both the Babylonians and Egyptians had rough numerical approximations to the value of pi, and later mathematicians in ancient Greece, particularly Archimedes, improved on those approximations.
https://www.scientificamerican.com/article/what-is-pi-and-how-did-it-originate/
And we have the Golden Ratio, phi, 1.618, which is recognized everywhere! Even in our bodies.
"Johannes Kepler wrote that "the image of man and woman stems from the divine proportion. In my opinion, the propagation of plants and the progenitive acts of animals are in the same ratio".
https://en.m.wikipedia.org/wiki/Golden_ratio
So, we consist of these patterns.