The May 20 1939 edition of the Toronto Daily Star contained this notice:
A Google search turned up a number of articles about the High Park Mineral Baths (nicknamed the “Minnies”). Torontoist and a Historic Toronto blog both provide a detailed history, and the Toronto Public Library has a number of photographs of the baths. BlogTO mentions the baths as part of an article on the history of High Park.
The baths were originally installed in 1913 as a part of the High Park Sanitarium, a facility that was affiliated with John Harvey Kellogg‘s Battle Creek Sanitarium. The sanitarium closed around 1922, but its owner, Dr. William McCormick, kept the mineral baths open. By 1924, they had expanded enough to host Olympic swimming and diving trials. The pools were closed in 1962 when part of their land was needed for the Bloor-Danforth subway.