In 1858 Curtius made a ceremonial visit to Edo as representative of the King William III of the Netherlands to pay tribute to Shogun Tokugawa Iesada. He was accompanied by his secretary Dirk de Graeff van Polsbroek, who left a description of the voyage to Edo in his diary. In Edo, Curtius found that the American Consul Townsend Harris had concluded the Treaty of Amity and Commerce, which gave the Americans a far more advantageous position for trade than what had been enjoyed by the Dutch. He therefore concluded a new treaty between the Netherlands and Japan based on the American treaty, with the additional clause that the use of "Fumi-e" to check for illegal Kirishitan at the Nagasaki magistrate would be abolished.