The Star of Venus is very difficult, and not well to be calculated, as
all Mathematicians and Astronomers will bear me witness; for its
course is found to be otherwise than that of the other six Planets, and
therefore its Birth is otherwise; ... Read more of Of The Spirit Of Copper at Occultism.ca
(Chessboard Problems)
Now, how many bishops are necessary in order that every square shall be
either occupied or attacked, and every bishop guarded by another bishop?
And how may they be placed?