What is the oldest written source in this country that mentions this right?
Cuba
The 2019 constitution protects personal and familial privacy in Article 48, the home in Article 49, and correspondence in Article 50 (Constitute Project, “Cuba 2019”). Privacy was not in the previous Cuban constitution of 1976 (Constitute Project, “Cuba 1976 rev. 2002”).
https://constituteproject.org/constitution/Cuba_2019?lang=en https://constituteproject.org/constitution/Cuba_2002?lang=en