This article investigates the development of land registry traditions in the medieval Mediterranean by examining a distinctive aspect of Latin, Greek and Arabic formularies used in boundary clauses. The paper makes particular reference to Islamic and Norman Sicily. The argument begins by recalling that the archetypal way of defining limits according to Classical Roman land surveyors was to begin 'ab oriente'. Many practices from Antiquity were discontinued in the Latin West, but the idea of starting with or from the east endured in many cases where boundaries were assigned cardinal directions. In the Byzantine Empire, the ‘Roman’ model was prescribed and emulated by Greek surveyors and scribes too. But in the Arab-Muslim Mediterranean, lands were defined with the southern limit first. This contrast forms the basis of a typology that can be tested against charter evidence in frontier zones – for example, in twelfth-century Sicily, which had been under Byzantine, Muslim and Norman rulers. It concludes that, under the Normans, private documents drawn up in Arabic began mainly with the southern limit following the ‘Islamic’ model. However, Arabic descriptions of crown lands started mainly in the ‘Romano-Byzantine’ way. These findings offer a higher resolution view of early Norman governance and suggest that such boundary definitions of the royal chancery could not have been based on older ones written in the Islamic period.