[1] Rhenius became secunde at the Cape Colony in August 1786 and after the departure of Cornelis Jacob van de Graaff was appointed acting governor on 24 June 1791.

[2] On the 2nd of March 1792, Rhenius signed a proclamation that formed the basis of the establishment of a postal service at the Cape Colony.

[3] He acted as governor until 3 July 1792, when authority was taken over by Sebastiaan Cornelis Nederburgh and Simon Hendrik Frijkenius, in their capacity as Commissioners-General.

In 1795 he was appointed Receiver-General and Treasurer and was also re-appointed as Commissaris-Politiek, a position he had held under the VOC.

He married Dorothea Hendriks Cruijwagen on 10 September 1786 and the couple had no children.