Similarly, did other contemporary figures from the Italian Renaissance (Machiavelli, Michelangelo, the Borgias, Caterino Sforza etc.) record their thoughts?
Hi, I wrote before about why it's very probable that Da Vinci knew about the Americas and that they are seperate from Asia, over here.
See also the other answer in that thread about connections between him, his patrons the Medicis, and Amerigo Vespucci.
Hopefully others can add more specifically on Da Vinci's writings and/or on the other Renaissance figured you mention which I'm less familiar with, hope this helps already.