Muesli was introduced around 1900 by the Swiss physician Maximilian Bircher-Benner for patients in his hospital, where a diet rich in fresh fruit and vegetables was an essential part of therapy. Muesli in its modern form became popular in western countries starting in the 1960s as part of increased interest in health food and vegetarian diets. Traditional muesli was eaten with orange juice and not milk.
Both apple pie spice and roasted cinnamon is available at Ralph’s and Krogers. Feel free to substitute regular cinnamon. Apple pie spice is a blend of cinnamon, nutmeg, and mace. For a delicious variation, substitute a grated pear for the apple or goji berries for the currants.