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

Italy

Under Article 48, any citizen, regardless of gender, who has attained majority is entitled to vote. The vote is free, secret, and a civic duty. The Chamber of Deputies is elected via universal suffrage, the Senate of the Republic is elected via regional voting, (Constitute Project, “Italy’s Constitution of 1947 with Amendments through 2020”).

Voting Rights and Suffrage · Country sources (all rights) · Years mentioned: 1947, 2020 · Last edited 2022-12-28 · Edit on GitHub