The invention of the shot tower enabled economical production of many nearly perfect lead spheres of the right size to fit in a musket.
Below is a chart with diameters per pellet and weight for idealized lead spheres.
Wire strands held a narrow platform, opposite which a one-tonne lead sphere counterrotated at the end of an adjustable arm.
The experimental apparatus consisted of a torsion balance with a pair of 2-inch 1.61-pound lead spheres suspended from the arm of a torsion balance and two much larger stationary lead balls (350 pounds), and Cavendish intended to measure the force of gravitational attraction between the two.
Majorana's experiments determined that mercury or lead around a suspended lead sphere acted as a screen and slightly decreased the Earth's gravitational pull.
Two 350-pound lead spheres placed nearby exerted just enough gravitational force to tug at the smaller balls, causing the dumbbell to move and the wire to twist.
This is not the weight of the rocket itself, but rather of a lead sphere whose diameter matches that of the rocket motor, officially defined as "The weight of a lead sphere that is just supported by a tube that the rocket motor will just fit into."
Sitting gaunt and bent on the tall stool, staring moodily at the long bright needle and the lead sphere, the old man didn't answer.
The arm stopped rotating when it reached an angle where the twisting force of the wire balanced the combined gravitational force of attraction between the large and small lead spheres.
A hollow space of about a thousand cubic inches remained in them, and in this space now, Aarn was arranging a lead sphere suspended from one arm of a long-arm balance.
