In 1592, Apostolos Valerianos, a Greek pilot in the service of the Spanish Crown, was sent north along the coast of America by the Viceroy of Mexico to find the Strait of Anian  -  first mentioned by Marco Polo as lying northeast of China. Valerianos, who was known by the Spanish as Juan de Fuca, sailed north to 47 degrees where he found a passage (possibly Juan de Fuca Strait) through which he sailed for 20 days. His description of the voyage was incorporated eventually into this 1752 map by Philippe Buache as the great inland sea, Mer de l'Ouest. Buache's map also introduced, for the first time, the de Fonte voyage which he placed to the north of the Mer de l'Ouest.