Collections of prayers for private devotional use appeared at least as early as the eighth century in the Insular world and shortly thereafter in the Carolingian Empire. In ninth-century English illuminated manuscripts, prayers began to be collected according to central devotional themes and were often accompanied by passages from the Gospels and the Psalms. Within the Carolingian and Ottonian milieux, series of prayers were often appended to Psalters, but without a thematic structure. Throughout the Middle Ages, prayer books supplemented the Psalter and the Book of Hours as volumes for devotional use. Prayer books grew in popularity during the later Middle Ages, a number containing fine illuminations having been produced for aristocratic patrons (such as Charles the Bold, Duke of Burgundy) in the fifteenth century.