Being a former catholic I can tell you used to be one of the favorite totures nuns used on us in school, said it strengthed the soul, as we would have to say the rosary over and over.
One very sadistic nun had a small triangle made that you had to kneel on. Later on I learned that in forms of martial arts it was used to strengthen the shins, for certain types of kicks. I had to endure hours of this punishment when in elementary school with those nuns. Found that if I did a mantra, a saying over and over the pain would dissipate, If those nuns only knew what I was really saying under my breath. I have found that the thinner and higher the object the more pain, through research ,