The letters upon which the book are based alledgedly provide a first-hand account by the Zeno brothers of a voyage of exploration undertaken in the year 1398 by a prince named Zichmni, who crossed the North Atlantic to Greenland and possibly reached North America. The authenticity of the account of the voyage is highly controversial, and many historians consider either the 1558 book, or the letters upon which it is based, to be a hoax.
Some later historians who credit the account as authentic have speculated that Zichmni was the Scottish nobleman Henry Sinclair. This identification is also considered to be highly controversial.[1]