Hidden in Plain Sight: The "Pietre di Paragone" and the Preeminence of Medieval Measurements in Communal Italy

In the squares of many Italian cities, unnoticed by most passersby, incisions carved in stone reproduce the dimensions of the measurements that were employed locally until 1861, when the nation endorsed the metric system. By gathering the evidence pertaining to these forms of display, this essay hopes to bring them back into historical consciousness. The story that follows is a rich one, for these carvings here called pietre di paragone performed many key functions in medieval society. Besides regularizing trade, they were at the center of a concordance of gazes and bodies, social rituals that contributed to the construction f collective identity, and the political establishment of he Italian communes. An investigation into the nexus between politics and measurements shows how the latter originated in the crumbling ofimperial uthority at the end of the tenth century. In addition, the political significance ofthe pietre is underscored by the tremendous attention that local authorities have paid to their preservation. These maneuvers lend weight to the cause of those scholars who challenge the idea of the Middle Ages as a dark, uncivilized ra. The Invention of the Middle Ages as Metrological Bedlam A seeming paradox informs our view of late medieval society in Italy. Even though from the eleventh century on, Italy enjoyed an economic boom, scholars are largely convinced that until the mid-fourteenth century Italians failed to develop reliable systems of measurement.1 Contributing to this misunderstanding is the fact that different units were used to measure products we today consider similar (for instance, the unit for silk was not the same as that for wool cloth). Also, many scholars assume that he dimensions of medieval measurements fluctuated over time, perhaps decreasing with the erosion of their metal standards.2 Thinking of the Middle Ages as lacking any coherent system of measurements has become such an ingrained habit that this deficiency has become in the popular consciousness one of the era's defining traits, one of those characteristics by which we distinguish, for instance, between medieval and modern times. With the present article, however, I want to reverse such claims by presenting evidence that will show that medieval systems of measurement were stable and scrupulously controlled and that regulation of measurements waned during the early Renaissance. Although many questions about the medieval genesis of metrological systems remain controversial (for example, what was the dimensional relationship GESTA 49/2 © The International Center of Medieval Art 2010 between classical, Carolingian, and medieval systems?), I argue that Italy's medieval measurements were standardized at the end of the tenth century. This move spurred economic regeneration and was particularly decisive for the consolidation of the communes, political associations between citizens created to safeguard their practical interests over those of the ruling aristocratic and ecclesiastical classes.3 The communes, whose origins and overall structure varied notably from city to city, established themselves throughout the twelfth century also against the interests of other organizations within the city. Internal as well as external competition required enforcement, and yet the communes trove to displace a sense of oppression on the part of the citizens by promoting a desire for societal action and representation. Measurements perfectly served this twofold purpose: they essentially worked as the communes' tools of control while (and because) citizens took them as the very source of egalitarian justice. Propelled by an active engagement with measurements, the medieval communes devised a revolutionary method to preserve these measurements, which I call pietre di paragone. This expression refers to series of grooves that reproduce the city's measurements incised on the facades of the cathedral, communal palace, or canopies in the center of one of the main squares (Figs. 1-5). Although many pietre still exist, today their presence is hardly noticed. When scholars mention them, it is in relation to mercantile practices, since the square that the pietre overlook usually was the site of the local market. While such a function is undeniable the pietre did allow standards to be checked during business transactions their role extended far beyond this one. This essay aims to address this shortcoming and thus restore the wide-ranging cultural impact of the pietre. Not only did they contribute o the political establishment ofthe commune, but they also generated a new perception of space. This revolution has gone undetected since the sixteenth century, that is, since the period that first gave a historical definition of medieval times. The Florentine Vincenzo Borghini (1515-1580) lamented that the measurements of his time were most unstable and confusing ("e si può dire generalmente la cosa delle misure, e de' pesi incertissima, ed instabilissima"), an effect, he claimed, of the despicable conduct of his ancestors, who were responsible for the disintegration of Rome's cultural system.4 Many shared his view: in modern treatises it is quite common to find a remark on measuring as a source of problems. Luca Pacioli (1446/47-15 17), the famous mathematician, went