Mythology of Crux
Crux was unknown to the ancient world, Ptolemy drew it as part of Centaur in the original 48 constellations, The Romans called it Thronis Caesaris in honor of emperor Augustus, although Crux is invisible in Italy, it was visible from Alexandaria.
Crux, the smallest of the constellations, was originally part of Centaurus. However, early voyagers sailing round the Cape of Good Hope in the sixteenth century decided that such a brilliant quartet of stars merited their own identity and they became known as CRUX. The Southern Hemisphere does not have a bright star near the south pole, so many used Crux which is some 25 degrees from true south. They would draw a line using the stars in the cross to the South Pole and could then make a determination of their position.