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

Oman

Under Article 58bis 9 of Oman’s Constitution, members of the Majlis Al Shura are elected through direct and secret votes. Citizens of Oman must be 21 or older to vote for these members. (Constitute Project, “ Oman’s Constitution of 1996 with Amendments through 2011”).

Voting Rights and Suffrage · Country sources (all rights) · Years mentioned: 1996, 2011 · Last edited 2022-12-28 · Edit on GitHub