In the mid-19th century, Friedrich Röber studied various Egyptian pyramids[lower-alpha 1] which he linked to the golden ratio.[8] This led pyramidologist John Taylor to theorize in his 1859 book The Great Pyramid: Why Was It Built and Who Built It? that the Great Pyramid of Giza is related to the golden ratio as well. Although the Great Pyramid's measurements have found to be within the margin of error, the connections between ancient Egypt and the golden ratio have been explained by modern scholars as coincidental, as no other knowledge of the golden ratio is known from before the fifth century BC.[9]