E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Cross and Ball,
so universally marked on Egyptian figures, is a circle and the letter \??\. The circle signifies the eternal preserver of the world, and the \??\ is the monogram of Thoth, the Egyptian Mercury, meaning wisdom.
The coronation orb is a sphere or ball surmounted by a cross, an emblem of empire introduced in representations of our Saviour. In this case the cross stands above the ball, to signify that the spiritual power is above the temporal.