Ferdinand Gregorovius, a 19th-century traveller and enthusiast of Corsican culture, reported that the preferred form of the literary tradition of his time was the "vocero", a type of polyphonic ballad originating from funeral obsequies. These laments were similar in form to the chorales of Greek drama except that the leader could improvise. Some performers were noted at this, such as the 1700s Mariola della Piazzole and Clorinda Franseschi. However, the trail of written popular literature of known date in Corsican currently goes no further back than the 17th century. An undated corpus of proverbs from communes may well precede it (see under "External links" below). Corsican has also left a trail of legal documents ending in the late 12th century. At that time the monasteries held considerable land on Corsica and many of the churchmen were notaries.