Use a yardstick or other long stick to stir until the Borax and washing soda powders are completely dissolved.
Use a tape measure or a string that you can then measure with a ruler or yardstick.
If you don't have a tape measure, use a piece of non-stretchable ribbon to "measure" and then hold the ribbon against a ruler, yardstick or metal tape measure to obtain your measurement.
Hold the string or tape against a yardstick to determine your actual bust measurement.
How a person dealt with that fear was the measure of their strength - and she was coming up short on the yardstick.