I'm a science/math journalist [ger] and currently I'm working on an article about prize money for open problems (Millennium Prize Problems and such). One section will be about the history of prize money and rewards. While I know about the culture of betting and rewards for open problems in the Lwow school and Erdös' faible for betting and rewarding, I wonder if there is a reliable source on the history of such rewards. In particular I'm interested in the question since when have money rewards for open problems started being a thing in mathematics and what some of the historic examples for such rewards are.
Thank you for helping me out :-)