it is unknown how the "tre cassyn" were originally adopted, and several theories have been put forward their origin. in 1607, english historian william camden stated that the "tre cassyn" were derived from the sicilian triskelion. in 1885 john newton considered the "tre cassyn" to have originated in the mid 13th century, when the pope offered the throne of sicily to edmund, son of king henry iii of england. newton noted that the wife of king alexander iii of scotland was henry's daughter, and that alexander visited the english court in 1255. later in 1266, norway ceded the isle of man to the kingdom of scotland, and newton considered it likely that alexander utilised the triskelion for the arms of his new possession. it has also been suggested that the ancestry of the "tre cassyn" can be traced to the triquetra in a coin of amlaíb cuarán, a 10th-century norse-gael warlord who was king of northumbria and king of dublin. lending credibility to this theory is the current belief that the mediaeval manx dynasty was related to that of amlaíb cuarán. however, the gap between the 10th century and late 13th century, when the "tre cassyn" is first recorded, is wide indeed, and it has been noted that several kings from this period are known to have borne a galley as their emblem, and not the "tre cassyn".