Cape Verde. The ship need not set out from Cape Verde and set sail constantly at West bearing to find it. Rather, it can sail out at a more convenient bearing (e.g. SW), and treat West as an "intended" course. So using the marteloio rule, it can sail on until the avanzar on the "intended" West course reaches 370 leagues. Indeed, it need not even set out from Cape Verde, but can set out from another place, say, Seville, and use the known distance and bearing of Cape Verde (viz. Seville) and the rule of marteloio to calculate when it has finally reached the Tordesillas meridian. This takes a couple of steps. Suppose Cape Verde (B on map) is 400 leagues Southwest of Seville (A on map), but the ship intends to go straight West from Seville to reach the Tordesillas meridian in the open sea. How long does it need to sail? The way to solve this by the rule of marteloio is to pose the problem in reverse: treat West as intended bearing and SW as the actual course. SW is four quarter-winds below W, so looking up the toleta for q = 4, the avanzar is 71 for every 100 miles sailed. So if a ship sailed 400 leagues on the "actual" SW course to Cape Verde, it would achieve an avanzar of 284 leagues (= 71 × 4) on the "intended" Westward course. Of course, the ship is not actually sailing SW to Cape Verde, but sailing W into the open sea. In other words, when the ship sets sail West from Seville, it knows it needs to sail 284 leagues on the West bearing before it reaches the implied Cape Verde meridian (point C on map), and should only start counting the 370 leagues to the Tordesillas line thereafter. In other words, it needs to sail a total of 284 + 370 = 654 leagues West of Seville to reach the Tordesillas line (point D on map). While this particular example shows the flexibility of the rule of marteloio, it also shows one of its principal drawbacks: the result completely ignores the curvature of the earth, i.e. the fact that the longitude meridian lines converge on the North Pole, and thus narrow at higher latitudes. Contrary to what the marteloio suggests, 370 leagues West of Cape Verde is not on the same longitude meridian as