During the early 15th Century, when a neighboring abbey claimed a portion of the land of Crowland Abbey (located in the Lincolnshire Fens of England) as its own, the Crowland monks presented legal authorities with a volume known as the Historia Crowlandensis
, or History of Crowland
, to document their historical ownership of the disputed lands. The History was accepted as legitimate, and the Crowland monks won their case. It wasn't until the 19th Century that historians realized the History was, for the most part, an invention. It contained numerous anachronisms, such as referring to monks who had supposedly studied at Oxford, long before the University was founded. It also claimed that many of the monks had lived to ages well past 100. Such longevity would be hard-to-believe today, let alone in the Middle Ages.
Hoaxes of the Middle Ages