Science fiction in Poland started in the late 18th century during the Polish Enlightenment, when Michał Dymitr Krajewski wrote a novel about the adventures of a Pole on the Moon. In the mid-19th century, during the age of romanticism in Poland, Adam Mickiewicz, reckoned by many to be Poland's top poet, also worked on a Verne-like science fiction novel "A History of the Future", but never published it (only a few fragments remain). Later in the same century, the period of positivism in Poland saw several writers explore themes similar to Verne and H.G. Wells, among them Władysław Umiński, Włodzimierz Zagórski and Sygurd Wiśniowski. However, perhaps the most famous Polish writer of the time, Bolesław Prus, used science fiction elements in his mainstream fiction. For example, his novel "Lalka" includes a "mad scientist" as well as a "lighter-than-air" metal. Similar themes are seen in the works of Prus's colleague, Stefan Żeromski, with his 'houses of glass' in "Przedwiośnie", and his death rays in "Róża".