Later in his life, he took up the collection of preserved papyri, largely from Egypt, and served as a benefactor and patron while working with the Oriental studies department of the University of Vienna.

In the course of the implementation of the 1861 February Patent constitution, he took up office as nominal Minister-President chairing the liberal cabinet of State Minister Anton von Schmerling.

Later in his life, Archduke Rainer became interested in the emerging science of papyrology, the study of preserved papyrus in the deserts of Egypt that offered primary source documents from centuries earlier.

In 1878–1879, the Viennese dealer in antiquities Theodor Graf [de] purchased recently found papyri from Faiyum, known as Arsinoe in the Hellenistic period.

Archduke Rainer continued to expand the collection with new purchases that Graf arranged, including papyri from digs at Hermopolis, Heracleopolis Magna, and other sites in the Faiyum area such as Soknopaiou Nesos.