The Mathematical Principles of Natural Philosophy, Book III: Of the System of the World
Proposition XV. Problem I
To find the principal diameters of the orbits of the planets.
They are to be taken in the sub-sesquiplicate proportion of the periodic times, by Prop. XV, Book I, and then to be severally augmented in the proportion of the sum of the masses of matter in the sun and each planet to the first of two mean proportionals betwixt that sum and the quantity of matter in the sun, by Prop. LX, Book I.