This post makes the claim:
Not bad you might think, but compare it to the Summerian Kù of 51.85cm of the copper of Nippur and its derived unit SAR of 3600 Kù being 1866.6 meter being only 0.77% off from an arc second of the meridian. Those ancient scientist did know the square root of 2 and PI by 4 sexagesimal figures. Thats better then IEEE floating point single precision! They did calculate the size of the earth being only 0.77% off the real value. All this wisdom was lost 333BC, when Alexander destroyed civilization, ...
My question is - what evidence is there to suggest that the ancient Sumerians calculated the square root of two?
Here's a paper on the topic. Apparently we know that they achieved this thanks to the YBC 7289 Yale Babylonian clay tablet. According to here, 4 sexagesimal figures is equivalent to 6 decimal places.