Factors affecting the time hourglass include: the amount of filler, the shape of the curve of the inner wall of the glass sphere (the chronological difference between the hourglass and the inverted hourglass), the width of the neck tube, the type and quality of the filler. The earliest hourglass used to use tomb marble powder, iron filings and eggshell powder. Modern hourglasses generally use artificially made glass beads. According to the German hourglass manufacturer KOCH's documentation, the 30-minute hourglass error can be controlled within 1 minute, and the hourly hourglass error is about 5 minutes. Note: It is not a timing instrument that can be compared to the accuracy of modern timing instruments.