There’s little documentation of the building process of Notre Dame, which began in 1163 and continued for about 200 years. Olivier de Châlus has devoted himself to teasing out the unwritten rules of construction — how builders decided the size of columns or the height of flying buttresses, for example. He notes that builders lifted 100-kilogram stones more than 60 meters off the ground without the benefits of modern technology. Exactly how this was accomplished has been lost to time, he says.
https://www.sciencenews.org/article/after-notre-dame-fire-scientists-glimpse-cathedral-origins
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