Complex sentence: The historian Alexandre Herculano discovered the manuscript in the library of the monastery in 1853 and transferred it to the national archives of Portugal in Lisbon to be part of the corpus of documents and texts in the history of Portugal ("Portugalliae Monumenta Historica").
Split into simpler sentences: The historian Alexandre Herculano discovered the manuscript in the library of the monastery in 1853 and transferred it to the national archives of Portugal in Lisbon. It is then intended to be part of the corpus of documents and texts in the history of Portugal ("Portugalliae Monumenta Historica").