1918 Swiss proportional representation popular initiative
The Federal popular initiative "Proportional representation of the National Council" was a Swiss popular initiative that was approved by the people and the cantons on October 13, 1918. == Proposal == The initiative proposed amending Article 73 of the Federal Constitution of Switzerland to make elections to the National Council direct and proportional instead of the majoritarian system then in place, and to use the cantons as electoral districts rather than electoral constituencies.
Source: Wikipedia — 1918 Swiss proportional representation popular initiative (CC BY-SA 4.0)