Barrier methods such as the condom have been around much longer, but were seen primarily as a means of preventing sexually transmitted diseases, not pregnancy. Casanova in the 18th century was one of the first reported using "assurance caps" to prevent impregnating his mistresses.[17][18] In 1909, Richard Richter developed the first intrauterine device made from silkworm gut which was further developed and marketed in Germany by Ernst Gräfenberg in the late 1920s.[19]