Cape Verde Islands. It did not specify the length of the league, its equivalent in equatorial degrees, or even which of the Cape Verde islands was intended. Instead, the treaty provided that these matters were to be settled by a joint voyage. This voyage never occurred, and instead there were only a series of nonbinding expert opinions produced over the next several decades. Their computations were further complicated by remaining uncertainty about the exact equatorial circumference of the earth. As such, each proposed line can be variously computed using geographical leagues defined in terms of a degree using a ratio which applies regardless of the size of the earth or using a specifically measured league applied to the actual equatorial circumference of the earth, with allowances necessary for the imperfect Portuguese and Spanish knowledge of its true dimensions. The earliest Aragonese opinion was provided by Jaime Ferrer in 1495 at the request of Ferdinand and Isabella. He stated to them that the demarcation line was 18° west of the most central island of the Cape Verde Islands, equivalent to 24°25′ west of Greenwich. (Harrisse concludes Ferrer must have meant Fogo as this central island.) Thus, Ferrer placed the line at 42°25′ W. on his sphere, which was 21.1% larger than the actual size of the earth. Harrisse further concludes from Ferrer's claim that his league contained 32 Olympic stades () that his lineif perfectly measuredwould have corresponded to a position west of Fogo at 47°37′ W. The earliest surviving Portuguese opinion is on the Cantino planisphere of 1501 or 1502, generally considered to represent the Portuguese standard map of its day. Because its demarcation line was midway between Cape Saint Roque, the northeast cape of South America, and the mouth of the Amazon River, labeled the Great River () with an estuary marked "All of this sea is fresh water" (), Harrisse computed that this line was at 42°30′ W. on the actual globe. Harrisse believed the large estuary just west of the line on the Cantino map was that of the Rio Maranhão (this estuary is now the Baía de São Marcos and the river is now the Mearim), whose flow is so weak that its gulf does not contain fresh water. In 1518, another Castilian opinion was provided by Martin Fernandez de Enciso. Harrisse computes that Enciso's sphere was 7.7% smaller than the actual size of the earth