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

Guinea-Bissau

According to Section II, Article 63, The President of the Republic is elected through universal, secret suffrage of the electing citizens. Electing citizens must be 18 years or older. (Constitute Project, “Guinea-Bissau’s Constitution of 1984 with Amendments through 1996”).

Voting Rights and Suffrage · Country sources (all rights) · Years mentioned: 1984, 1996 · Last edited 2022-12-28 · Edit on GitHub