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

Dominica

Under Chapter III, Part 1, any resident who is a birthright citizen or naturalized citizen of Dominica and is over the age of 18 has a right to suffrage via a secret and unimposed ballot unless this right has been taken away by Parliament. (Constitute Project, “Dominica’s Constitution of 1978 with revisions through 2014).

Voting Rights and Suffrage · Country sources (all rights) · Years mentioned: 1978, 2014 · Last edited 2022-12-28 · Edit on GitHub