- The Archimedes principle is as follows: In the privacy of her bathroom the patient will immerse each breast separately into a large pot filled to the brim with tap water. The breast will displace some of the water which will be collected into another larger container e.g. plastic dish pan placed underneath the pot. The patient will be asked to measure the volume of the displaced water in ml. The volume that will be displaced will approximate the weight of the breast. The measurement will be done 3 times and the average for each breast will be recorded.