Natural Histories A Philosophy of Falcons Frederick II, Holy Roman Emperor, was obsessed with falconry. This led him to write a truly revolutionary book on the subject. Alexander Lee | Published in History Today Volume 71 Issue 10 October 2021 A gyrfalcon. 18th-century coloured engraving, by François-Nicolas Martinet © Getty Images. To continue reading this article you will need to purchase access to the online archive. Buy Online Access Buy Print & Archive Subscription If you have already purchased access, or are a print & archive subscriber, please ensure you are logged in. Please email firstname.lastname@example.org if you have any problems.