 Abad y Queipo presented Humboldt with his published writings when the cleric visited Paris in 1806.Humboldt's "Political Essay on the Kingdom of New Spain" was one of his first publications from his five-year sojourn to Spanish America and drew heavily on Abad's memorials.Humboldt took Abad y Queipo's argument about the low condition of Mexico's indigenous population as impeding progress in the viceroyalty, which Abad had first mentioned in a 1799 memorial to Bishop Antonio de San Miguel.