>written records comes via contemporary visitors from much different cultures

that isn't necessarily bad, anyway in the context of your post reminded of

https://en.wikipedia.org/wiki/Ahmad_ibn_Fadlan

"10th-century Arab traveler from Baghdad, Abbasid Caliphate,[a] famous for his account of his travels as a member of an embassy of the Abbasid caliph al-Muqtadir to the king of the Volga Bulgars, known as his risāla ("account" or "journal").[b]

His account is most notable for providing a detailed description of the Volga Vikings, including eyewitness accounts of life as part of a trade caravan and witnessing a ship burial. "