The Cardinal Vicar of Pope Pius XI
‘We recall that a dress cannot be called decent which is cut deeper than two fingers breadth under the pit of the throat, which does not cover the arms at least to the elbows, and scarcely reaches a bit beyond the knee. Furthermore, dresses of transparent material are improper. Let parents keep their daughters away from public gymnastic games and contests; but, if their daughters are compelled to attend such exhibitions, let them see to it that they are fully and modestly dressed. Let them never permit their daughters to don immodest garb.’
The Sacred Congregation of the Council (by the mandate of Pope Pius XI), January 12, 1930 A.D.