What is the oldest written source in this country that mentions this right?

Ghana

In the 1992 constitution, still in force today, the right to privacy in the home and correspondence is found in Article 18(2) (Constitute Project, “Ghana 1992 rev. 1996”).

https://constituteproject.org/constitution/Ghana_1996?lang=en

Privacy Rights · Country sources (all rights) · Years mentioned: 1992, 1996 · Last edited 2022-12-28 · Edit on GitHub