The Egyptians didn't really write too terribly many documents on HOW certain things were done, just that things WERE done. We do have plenty of physical evidence as to what they utilized though. There are a good number of extent records for educational crafts though. We know how they did math, including all the steps to get to an answer. We can see how their medical practices worked as well.
It's also worth noting that the library of Alexandria was constructed closer to the modern day than it was to the election of the pyramids. It would still have had a huge amount of information regarding the hellenistic world though.