The centre of the world and the centre of the earth's weight
Why heavy bodies seek the centre, and why earth-and-water is the centre of the spheres
A page of continuous prose in mirror script arguing about the centre of the cosmos. Leonardo reasons that the centre of the world cannot be the centre of the 'universal circles' traced by the shining stars unless the parts of the earth surrounding that centre are of equal weight and distance. He asserts that every heavy body is driven toward the centre, and concludes that the combined centre of weight of the earth and its water is the centre of the celestial spheres, distinct from the geometric centre of the world's mass.
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Every heavy body is driven toward the centre
Leonardo states that naturally every ponderous thing is pushed toward the centre, because the centre lies most remote from the 'repellent and circular expellers.' The argument treats weight as the force that gathers matter about a single point.
The centre of the world versus the circles of the stars
The centre of the world, he argues, cannot coincide with the centre of the universal circles made by the course of the shining stars unless the surrounding parts of the earth are of equal weight at equal distance. The reasoning links the earthly centre to the geometry of the heavenly spheres.
Earth-and-water as the centre of the spheres
He concludes that the centre of the weight of the earth taken together with the water is the true centre of the spheres, and not the centre of the mass of the world. The body of the earth is thus weighed as a physical mass distinct from an abstract cosmic point.