Galileo Thermometer, the kind invented by the man himself, and the first objective means of measuring temperature. It's a beautiful object as well. The floating coloured balls in the special liquid (paraffin oil base) are calibrated to fall as the temperature rises - the lowest floating ball shows the correct temperature (within 2 degrees C.). Best kept indoors out of continuous direct sunlight.
Three sizes are available:
28cm tall (desktop): 6 balls; temp range 18 - 28 C
44cm tall: 10 balls, temp range 16 - 34 C
56cm tall: 11 balls, temp range 16 - 36 C