Let's not forget that variation on the blinding action that rulers also used to not only make the person physically not able to usurp the crown, but also make it so they would not want to mentally either: Blinding and castrating. Professor Knox states this in the third section when talking about Italy during the time period of the third-fourth crusades. In the section titled, "Italy during the Crusades: Sicily under the Hohenstaufen" Professor Knox states that when Henry, King of Italy and Germany makes a move against Tancred in Sicily, after defeating and killing Tancred finds Tancred's son, and "captured the boy and had him blinded and castrated"
1 It seems when I hear about people castrating other people, it is in the context of the castratee being young, meaning a very small child. It would seem they would probably do this so that it will have the effect of Eunuchs in the Asian courts. The person would grow up without so much testosterone and would not want the throne for themselves.
Interestingly enough, this practice goes back before even 1000 A.D. I found a journal article that states, "A particularly instructive episode is handed down to us by Thietmar of Merseburg: when Boleslaw III of Bohemia feared that his brothers Jaromir and Udalrich had planned an uprising against him, he had Jaromir castrated and tried to have Udalrich killed." So not only was blinding an occurance in Europe from time to time, but so was castrating and blinding your opponents.
21. E.L. Skip Knox, "Italy during the Crusades: Sicily under the Hohenstaufen," The Crusades, http://boisestate.edu/courses/crusades/ ... y/03.shtml (accessed March 10, 2010).
2. Klaus van Eickels, "Gendered Violence: Castration and Blinding as Punishment for Treason in Normandy and Anglo-Norman England," Gender & History 16, no. 3 (November 2004): 588-602, Academic Search Premier, EBSCOhost (accessed March 10, 2010).