The first pre-contact solar eclipse in Seneca country occurred June 28, 1451.
Mann believes that Wallace did not dare risk an earlier date because of the academic politics of the late 1940s. had invented wampum -- a back-bone artifact of the League!
In an academic paper titled "A Sign in the Sky: Dating the League of the Haudenosaunee," Mann estimates that the journey of Deganawidah (The Peacemaker) and Hiawatha in support of the Great Law had begun about a quarter-century earlier with the Mohawks, at the "eastern door" of the Confederacy, about 25 years earlier.
All three precedents have been cited as forerunners of the United States system of representative democracy.
The Haudenosaunee Confederacy functions today in Upstate New York; it even issues passports.
In her paper, Mann suggests that Wallace knew enough of the Senecas' oral history to realize that a solar eclipse was a key element to determining the founding date.
Wallace also was fluent in German, the language in which he would need to read T. Oppolzer's Canon der Finsternisse, the best historical eclipse tables available at the time.