Complex sentence: The visual particularity of bare feet was a sufficient attribute to distinguish prisoners from free citizens practically effortless, it was therefore widely used to display the state of captivity and imprisonment in most civilizations of the past.
Split into simpler sentences: The visual particularity of bare feet was a sufficiently noticable to distinguish prisoners from free citizens. As it was achieved practically effortless, it was common practice to display the state of captivity and imprisonment in most civilizations of the past.