Falsehood flies, and Truth comes limping after it;<br /> —Jonathan Swift, “The Examiner, From Thursday Nov 2 to Thursday Nov 9, 1710.” In The Examiner [Afterw.] The Whig Examiner, edited by Joseph Addison and Jonathan Swift, Vol. 15. London: John Morphew, near Stationers Hall, 1710.

found via https://quoteinvestigator.com/2014/07/13/truth/

with variations on "A lie travels around the globe while the truth is putting on its shoes." attributed variously to Mark Twain, Jonathan Swift, Thomas Francklin, Fisher Ames, Thomas Jefferson, John Randolph, Charles Haddon Spurgeon, Winston Churchill, Terry Pratchett?

Addison, Joseph, and Jonathan Swift. The Examiner [Afterw.] The Whig Examiner. London: John Morphew, near Stationers Hall, 1710.

"Nullum numen abest si sit prudentia, is unquestionably true, with regard to every thing except poetry; and I am very sure that any man of common understanding may, by proper culture, care, attention, and labour, make himself whatever he pleases, except a good poet." Chesterfield, Letter lxxxi.

See also: https://en.m.wikisource.org/wiki/Page:The_Works_of_the_Rev._Jonathan_Swift,_Volume_5.djvu/261 as a source

Swift, Jonathan. The Works of the Rev. Jonathan Swift. Edited by Thomas Sheridan and John Nichols. Vol. 5. 19 vols. London: H. Baldwin and Son, 1801.

A line in the margin doesn't fit with any mnemotechniques I'm aware of, so it's more likely a method to indicate what he had read, and up to what point. Likely not an indicator of storage to memory.

“The Hare and Many Friends” is the final poem in John Gay’s collection of fables written in 1727 for Prince William, Duke of Cumberland. This collection is commonly known as Fables, but it is also known as Fifty-one Fables in Verse or Fables of John Gay. Gay’s poem opens with: “Friendship, like love, is but a name,/Unless to one you stint the flame.” The poem concerns the inconstancy of friendship, as exemplified by a hare that lives on friendly terms with a group of farm animals. The hare is refused help by each of the animals as she begs them to help her escape an approaching hunter. Each of the animals gives her a different excuse of why they cannot help, eventually leaving the hare to her death at the hands of the hunter.

“A hare, who, in a civil way, Complied with ev'ry thing, like Gay, Was known by all the bestial train, Who haunt the wood, or graze the plain: Her care was, never to offend,<br> And ev'ry creature was her friend.”

The poem is intended to teach readers that one with many friends has no true friends, so it is better to be close friends with a few than friends with many. However, beyond the lesson of friendship, there is a darker moral lesson in the poem intended specifically for the young women reciting it. Gay creates a connection between friendship and romantic love that sets up the poem as a description of the fatality that awaits women (symbolized by the hare) if they associate with the wrong people and lose their reputations. This foreshadows the risks that readers will witness Catherine experience in her new environment when she journeys to Bath.

Both at the time of publication and for some 150 years afterwards, the poem won widespread popularity. Despite this widespread popularity, Gay’s hopes of Court preferment were disappointed and the story was put about by his friends that the fable had a personal application. Jonathan Swift in particular wrote “Thus Gay, the Hare with many friends,/Twice seven long years at court attends;/Who, under tales conveying truth,/To virtue formed a princely youth;/Who paid his courtship with the crowd,/As far as modish pride allowed;/Rejects a servile usher’s place,/And leaves St. James’s in disgrace.” (Heneage Jesse 88). But after a prose version appeared in a collection of Aesop’s Fables, Gay’s original authorship gradually slipped from the public memory. Nevertheless, Gay’s Fables went through repeated editions, and “The Hare and Many Friends” stood out as a particular favorite. As Austen’s narrator notes, it was a common recitation piece for children and was frequently shown off as part of a young lady’s accomplishments.

See this illustration by John Wootton of "The Hare and Many Friends."

Examples of this sort of non-logical behaviour used to represent identity can be found in fiction in:

• Dr. Seuss' The Butter Battle Book (Random House,1984) which is based on
• the war between Lilliput and Blefuscu in Jonathan Swift's 1726 satire Gulliver's Travels, which was based on an argument over the correct end to crack an egg once soft-boiled.

It almost seems related to creating identity politics as bike-shedding because the real issues are so complex that most people can't grasp all the nuances, so it's easier to choose sides based on some completely other heuristic. Changing sides later on causes too much cognitive dissonance, so once on a path, one must stick to it.