Advertisement flyer by the publisher "Verlag Es Werde Licht". Mentioned books: "Hellsehen" which I have never seen, "Magische Phänomene" and "Das Universum der Magie".
This is a list of patents (see attached file) that I was able to research in the Berliner Patentamt. Unfortunately only the numbers were available but the documents themself could not be found.
This magic magazine from 1908 was published in London and contains a picture of Conradi Horster on the front page, a short article and an advertisement ad.
This magazine from 1930 contains an article about magic and Horsters "Maja - Vereinigung für magische Kunst". It is targeted to teenagers.