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

Guatemala

Under Chapter II, any citizen, by definition over 18 years of age, has the freedom of suffrage. Citizens may cast secret ballots to elect the Congress of the Republic, President, and Vice-President. (Consitute Project, “Guatemala’s Constitution of 1985 with Amendments through 1993”).

Voting Rights and Suffrage · Country sources (all rights) · Years mentioned: 1985, 1993 · Last edited 2022-12-28 · Edit on GitHub