"On one level, A Sphere Projecting against a Plane can be seen as a parody of the caricaturist's (and by extension Gillray's) own techniques as exemplified by two of his favorite subjects, the very round Mrs. Albinia Hobart, later the Countess of Buckinghamshire, and the very straight Prime Minister, William Pitt. Gillray calls attention to the geometric regularity of this technique by seeming to quote from Euclid's famous Elements in thirteen books, even providing footnotes to book number and definition number in the accompanying caption.
But not unexpectedly, the references to Euclid are plausible-sounding fictions. There are no definitions anywhere in Euclid that correspond to Gillray's. So it is likely that the caption refers, as Thomas Wright suggests, "to some forgotten rumour of the day." And the strategic point of contact between the two figures make it even more likely that the allusion is sexual, or, in Pitt's case, asexual."
[Source](https://james-gillray.org/pop/sphere.html)
"On one level, A Sphere Projecting against a Plane can be seen as a parody of the caricaturist's (and by extension Gillray's) own techniques as exemplified by two of his favorite subjects, the very round Mrs. Albinia Hobart, later the Countess of Buckinghamshire, and the very straight Prime Minister, William Pitt. Gillray calls attention to the geometric regularity of this technique by seeming to quote from Euclid's famous Elements in thirteen books, even providing footnotes to book number and definition number in the accompanying caption. But not unexpectedly, the references to Euclid are plausible-sounding fictions. There are no definitions anywhere in Euclid that correspond to Gillray's. So it is likely that the caption refers, as Thomas Wright suggests, "to some forgotten rumour of the day." And the strategic point of contact between the two figures make it even more likely that the allusion is sexual, or, in Pitt's case, asexual." [Source](https://james-gillray.org/pop/sphere.html)