The biographer Alexander Wheelock Thayer believes that Mozart's rivalry with Salieri could have originated with an incident in 1781, when Mozart applied to be the music teacher of Princess Elisabeth of Württemberg, and Salieri was selected instead because of his reputation as a singing teacher. The following year Mozart once again failed to be selected as the princess's piano teacher. "Salieri and his tribe will move heaven and earth to put it down", Leopold Mozart wrote to his daughter Nannerl. But at the time of the premiere of "Figaro", Salieri was busy with his new French opera "Les Horaces". In addition, when Lorenzo Da Ponte was in Prague preparing the production of Mozart's setting of his "Don Giovanni", the poet was ordered back to Vienna for a royal wedding for which Salieri's "Axur, re d'Ormus" would be performed. Obviously, Mozart was not pleased by this.