A 16th century Portuguese map shows “signs of hearsay knowledge of the Great Lakes.”
James Robert Enterline, https://www.google.com/books/edition/Erikson_Eskimos_and_Columbus/Pr-s7MrkBW8C?hl=en&gbpv=1&dq=%22Kunstmann%20III%22&pg=PA248&printsec=frontcover, gives the date as “Sometime between 1503 and 1511” and remarks that it shows “signs of hearsay knowledge of the Great Lakes.”
Other comments about the map were written by Bruno Almeida for a research project at the University of Lison: https://www.medea-chart.org/single-post/chart-of-the-week-the-kunstmann-iii-chart-1501-1502-anonymous-portuguese
The land is labeled “Terra de cortte Real”. The Corte Reals were a family of Portuguese explorers: https://epe.lac-bac.gc.ca/100/206/301/lac-bac/explorers/www.collectionscanada.gc.ca/explorers/h24-1320-e.html
The squiggly line near the bottom depicts an anticipated water route across the continent to the western ocean, which was still anticipated in the days of Jean Nicolet, motivating his journey to Wisconsin in 1634.
Map-related posts
https://doorcounty.substack.com/t/maps