Speculum nauticum [electronic resource] : A looking glasse, for sea-men: wherein they may behold a small instrument called plaine scale: whereby all questions nauticall, and propositions astronomicall are very easily and demonstratiuely wrought. / Lately penned, and now published for the vse and benefot of such as will make good vse of it. By Iohn Aspley student in physicke, and practitioner of the mathematickes, in the city of London.