The concept of the ball game was understood in the Early Middle Ages (600–1066). Writing in the 9th century, Welsh monk and historian Nennius makes reference in his book Historia Brittonum to "the field of Ælecti, in the district of Glevesing, where a party of boys were playing at ball". This account was attributed to a 5th-century source that has not survived. Ball games may have been played throughout the 1st millennium despite a lack of documented evidence. Oral traditions from the West Country and South East Wales assert that the games of Cornish "Hurling to Country" and "Hurling to Goals", Devon "Out-Hurling" and Welsh "Cnapan" played during Christian festivals have more ancient Celtic origins. The wooden balls used in these games are only found in regions where Celtic culture is still venerated. These communal events may even have started with prehistoric workers hurling forward carved wooden balls or stone balls that archaeologists have theorised could have been used to move megaliths in stone circle construction. Records from antiquity have survived relating to various ball games played by the Romans, notably Harpastum which contained many elements that feature in the Shrovetide ball game. These influences were available to a Catholic Church Clergy familiar with native customs and educated in Latin when a ball game was introduced to Shrovetide festivities.