As members of hereditary learned families Mícheál Ó Cléirigh and his collaborators ('the Four Masters') used many medieval Irish manuscripts as sources for their history of Ireland and its saints. These manuscripts belonged to their own families or to others in their learned network. They stressed the authenticity of their history by frequently quoting medieval sources.
Among the great Irish books of seanchas was the Book of Leinster, which contained many early Irish texts including the calendar of saints known as the Martyrology of Tallaght. Mícheál Ó Cléirigh obtained that portion of the Book of Leinster and used it as a source for his own compilation the Martyrology of Donegal. The Four Masters chose to follow the medieval Irish tradition of recording history in the form of chronicles and in doing so they consulted earlier annals such as the Annals of Ulster and similar texts that no longer survive today.
Section 1 consists of a selection of the range of medieval sources available during the seventeenth century.
