When measuring the mass of an object, it's important to remember that mass and weight, though sometimes confused with one another, are not the same things. An object may weigh less on a planet with a lower gravitational pull, but it will still contain the same amount of matter. The simplest way to measure the mass of an object, such as a lead fishing sinker, is to use a triple beam balance.
Calibrate the beam to make sure it is properly balanced. Slide all the weights back toward the pan, and make sure the indicator is aligned exactly to the balance mark. Raise or lower the pointer to align it by turning the zero-adjust knob under the pan.
Place the fishing sinker on the pan. This will cause the indicator to rise above the balance mark.
Slide the weight on the middle beam toward the right, settling within the notches, until the indicator points to the balance mark or below it. If it points to the balance mark, you've found the mass. If it points below the mark, slide the weight back one notch.
Slide the weight on the rear beam along the notches toward the right until the indicator points to the balance mark or below. If it points below, slide the rear weight one notch back.
Adjust the front weight toward the right. There are no notches so this weight can slide freely and settle anywhere on the beam. Slide it until the indicator rests exactly on the balance mark.
Add up the weights on all three beams indicated by the weights' position on the beams. The middle beam indicates grams by the 100s, the rear by the 10s, and the front by the gram with the tick marks indicating tenths of grams. The sum of all three beams is the mass of your fishing sinker.