Calculations

This illustration is part of the work entitled Brief Compendium of the Sphere and the Art of Sailing With New Instruments and Rulers Exemplified With Very Subtle Demonstrations (Breve Compendio de la Esfera Y de la Arte de Navegar Con Nuevos Instrumentos Y Reglas Ejemplificado Con Muy Sutiles Demostraciones), compiled by Martín Cortés and first published in Seville in 1551.