"Ut pendet continuum flexile, sic stabit contiguum rigidum inversum -- As hangs a flexible cable, so inverted stand the touching pieces of an arch." (although t

"Ut pendet continuum flexile, sic stabit contiguum rigidum inversum -- As hangs a flexible cable, so inverted stand the touching pieces of an arch." (although they figured out at some point that this curve was close to being a parabola)