Adelard of Bath, "England's first scientist" (flourished 1110-1150) studied in Arabic-speaking lands, returning to England with knowledge of the astrolabe. Artisans produced some the size of finger-rings, having two concentric, moveable layers of metal. Adjusting the outer ring to month-specific calibrations on the inner ring let the wearer tell the time and, more importantly, the length of remaining daylight, ensuring that the wearer of such a ring would never be "benighted." Such rings were often engraved "carpe diem," seize the day!