The mathematician and philosopher, Bernard Bolzano, entrusted his unfinished work, Grössenlehre ("Theory of Quantity", a philosophical foundation for mathematics), which had not been completed at the time of his death in 1848, to von Zimmermann who was 24 years old. Zimmermann had been a student of Bolzano's. Since Zimmermann's interests were more in the area of philosophy as he had been appointed to the chair of philosophy at the University of Prague in 1852, he didn't do much with Bolzano's papers. Most of the remaining manuscripts stayed in Zimmermann's possession until 1882 when he gave them to the Austrian Academy of Sciences (Kaiserliche Akademie der Wissenschaften in Wien).
^von Schlosser, Julius, "The Vienna school of the history of art". Cf. pp.27, 29. (translated into English and edited by Karl Johns from ‘Die Wiener Schule der Kunstgeschichte‘, Mitteilungen des österreichischen Institut für Geschichtsforschung Ergänzungs-Band 13, Heft 2, Innsbruck: Wagner 1934)