Esmeraldo de Situ Orbis is an early modern work on cosmography and Atlantic exploration written by the Portuguese geographer and navigator Duarte Pacheco Pereira. It was dedicated to King Manuel I of Portugal (1495–1521). The work was divided into five parts with a total of fifty nine chapters and around two hundred pages. Composed in 1506, it dealt, in the author’s own words, with “cosmography and seafaring”. The enigmatic title name appears to be a mixture of Portuguese and Latin. It was written in Portuguese and it featured geographical coordinates for all known ports at the time. The manuscript was most likely written between 1505 and 1508 and was finished by 1508. Synopsis Esmeraldo de Situ Orbis describes itself as "a book of cosmography and navigation". It states that, in addition to the continents of Europe, Africa, and Asia, the world had a "fourth part": i.e., America. Eviatar Zerubavel explains that, according to Pacheco Pereira, America encompassed both North and South America. According to Joaquim Barradas de Carvalho, when Pacheco Pereira composed the Esmeraldo, he was familiar with texts including Sacrobosco’s De sphaera mundi and Pliny’s Natural History. The four books The work is divided into four books, combined in a single volume: Prologue First Book: Discoveries of Henry the Navigator – 33 chapters Second Book: Discoveries of Afonso V – 11 chapters Third Book: Discoveries of John I – 9 chapters Fourth Book: Discoveries of Manuel I – 6 chapters Duarte Pacheco Pereira references some maps that have disappeared. It is not clear whether the Esmeraldo was ever finished; it mentions a fifth book, and only a portion of the fourth appears complete in the existing manuscripts. Study by Jorge Couto According to a study by the Portuguese historian Jorge Couto of the University of Lisbon, the work was lost for four centuries due to the confidential nature of its content. The title was decrypted as: "Esmeraldo" - an anagram of the initials in Latin of the names of Manuel (Emmanuel), the ruler and Duarte (Eduardus), the explorer. De Situ Orbis means "on the Geography of the Globe (the Earth)", the title of a work by Pomponius Mela, an early Roman scientist and prominent geographer who inspired Duarte Pacheco Pereira. Manuel I considered the nautical, geographical and economic information contained in the work so valuable that he never allowed public access. The work consists of a detailed account of