The absence of preserved Etruscan literature makes the study of the Etruscans a preeminently archaeological exercise. However, it is almost certain that such texts existed at least in later periods, particularly to mark the achievements of descent groups and cities and to define the proper practice of the disciplina etrusca. The closest surviving example of such a text is the linen wrapping of the Zagreb mummy, which records a ritual calendar.
Historical Dictionary of the Etruscans. Simon K. F. Stoddart.