rule of Marteloio
... that Italian sailors in the Middle Ages used trigonometry and the rule of Marteloio to navigate at sea?
... that Italian sailors in the Middle Ages used <a href="./Trigonometry" id="mwDNk" rel="mw:WikiLink" title="Trigonometry">trigonometry</a> and the <b id="mwDNo"><a class="mw-redirect" href="./Rule_of_Marteloio" id="mwDNs" rel="mw:WikiLink" title="Rule of Marteloio">rule of Marteloio</a></b> <i id="mwDNw">(pictured)</i> to navigate at sea?