We begin this journey with a book written in 1919 titled: "Influenza; a study of measures for the control of the epidemic"

This book was written in regard to the "Spanish flu epidemic" of 1918.
Link to book:

books.google.com/books?id=R_o1A… As we can see, starting on page 12 this book addresses the mask mandates put in place in major cities at the time and compared their effect to cities with no such mandate. The conclusion was that masks where ineffective.