Recently, I watched a show whith my girlfriends father where a descendant of Jacob Fugger was interviewed. He said something along the lines of: "In his time, he was probably the richest man who has ever existed." I responded that there have been a few richer people, among them was Mansa Musa. When I mentioned that he was a king of Mali, he quickly brushed everything off as a tale. He said that "sources from Africa are not reliable" and "are frequently mythologized", but the sources about Fugger are reliable. However, as far as I can tell (and please correct me if I am wrong), the scientific consenus seems to be that Mansa Musa really *was* the richest person in human history.

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Now my question is, how do we actually know that he was responsible for an economic crash in Egypt? How do we know that the sources about him are reliable / how do we know *which* sources about him are reliable?