The November 22 1946 edition of the Toronto Globe and Mail contained this short article about a man who planned to cross Niagara Falls on a tightrope:
He doesn’t appear to have done it – this page on Nik Wallenda claims that he was the first to do it in 2012, and this B&B Niagara page lists nine Niagara Falls gorge walkers, none of whom was Mr. Trostl.
A search for “The Great Arturo” and “Arturo Trostl” turned up two links:
David Niven also played “Tony, the Great Arturo” in the 1939 film Eternally Yours, but that appears to be unrelated.
The Trostl family’s lives were marred by two tragedies: daughter Eve perished in a circus accident in 1951, and son Arthur Jr. was seriously wounded by a bomb planted by the Alphabet Bomber in the Los Angeles airport in 1974. The Great Arturo passed away in 1998.