 Although he was the Margrave and Prince-elector of Brandenburg and the Duke of Prussia, Frederick desired the more prestigious title of king.However, according to Germanic law at that time, no kingdoms could exist within the Holy Roman Empire, with the exception of the Kingdom of Bohemia which belonged to the Holy Roman Emperor.In the Crown Treaty of 16 November 1700, Frederick persuaded Leopold I, Archduke of Austria and Holy Roman Emperor, to allow Prussia to be elevated to a kingdom.