German scientist Alexander von Humboldt (1769--1859) did not know or use the modern term "space weather." Nevertheless, several corresponding phenomena, such as the Sun and sunspots, geomagnetism, and aurorae, are extensively discussed in his famous work Kosmos, a set of five volumes published between 1845 and 1962. Humboldt, who studied at universities in Frankfurt/Oder, G¿ttingen, Hamburg, Freiburg, and Jena, was already an acknowledged scholar when he wrote Kosmos, and kept close and lively contact with the most influential scientists of his time. Therefore his work is a thorough review of the knowledge at the middle of the nineteenth century.