"[W]e are uncertain as to the time and place of [the] introduction [of these numeral forms] into Europe. There are two general theories... The first is that they were carried by the Moors to Spain in the eighth or ninth century, and thence were transmitted to Christian Europe... The second, advanced by Woepcke, is that they... were already in Spain when the Arabs arrived there, having reached the West through the Neo-Pythagoreans. There are two facts to support this second theory: (1) the forms of these numerals are characteristic, differing materially from those which were brought by Leonardo of Pisa from Northern Africa early in the thirteenth century (before 1202 a.d.); (2) they are essentially those which tradition has so persistently assigned to Boethius (c. 500 A.D.), and which he would naturally have received, if at all, from these same Neo-Pythagoreans or from the sources from which they derived them."