text: In the report, he described the peculiarities of the Mongol Empire as well as many geographical observations. There were also anthropological observations, such as his surprise at the presence of Islam in Inner Asia. William was critical of the Hellenic traditions he encountered among the Christians of the former Byzantine Empire, including the Nicaean celebration of a feast day for Felicitas, which he reports was known to John III Doukas Vatatzes through the alleged possession of the second half of Ovid's incomplete Book of Days.
  William also answered a long-standing question in demonstrating by his passage north of the Caspian Sea that it was an inland sea and did not flow into the Arctic Ocean; although earlier Scandinavian explorers like Ingvar the Far-Travelled had extensive knowledge of the region, William was the first to answer the question in written form.
  William's report is one of the great masterpieces of medieval geographical literature, comparable to that of Marco Polo, although they are very different. William was a good observer and an excellent writer. He asked many questions along the way and did not take folk tales and fables as literal truth. He showed a great facility with language, noting the similarities between those he encountered and those European languages he already knew.