 Humboldt also consulted other German mining experts, who were already in Mexico.While Humboldt was a welcome foreign scientist and mining expert, the Spanish crown had established fertile ground for Humboldt's investigations into mining.Spanish America's ancient civilizations were a source of interest for Humboldt, who included images of Mexican manuscripts (or codices) and Inca ruins in his richly illustrated "Vues des cordillères et monuments des peuples indigènes de l'Amerique" (1810–1813), the most experimental of Humboldt's publications, since it does not have "a single ordering principle" but his opinions and contentions based on observation.