After the marriage of King João VI's eldest son and Brazil's first Emperor, Dom Pedro I (1798–1834), to H.I. & R.H. Archduchess Maria Leopoldina of Austria (1797–1826), the Museum started to attract some of the greatest European naturalists of the 19th century, such as Maximilian zu Wied-Neuwied (1782–1867), Johann Baptist von Spix (1781–1826), and Carl Friedrich Philipp von Martius (1794–1868). Other European researchers who explored the country, such as Augustin Saint-Hilaire (1799–1853) and the Baron von Langsdorff (1774–1852), contributed to the collections of the Royal Museum.