“All things must needs be borne on through the calm void moving at equal rate with unequal weights.”
Book II, lines 238–239 (tr. Bailey)
De Rerum Natura (On the Nature of Things)
Original
Omnia qua propter debent per inane quietum aeque ponderibus non aequis concita ferri.
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Lucretius 45
Roman poet and philosopher -94–-55 BCRelated quotes

“Votes go by number, not weight; nor can it be otherwise in assemblies of this kind, where nothing is more unequal than that equality which prevails in them.”
Numerantur enim sententiae, non ponderantur; nec aliud in publico consilio potest fieri, in quo nihil est tam inaequale quam aequalitas ipsa.
Letter 12, 5.
Letters, Book II

“The worst form of inequality is to try to make unequal things equal.”
Whilst a paraphrase this is based off of Aristotle's writings as Aristotle stated "For instance, it is thought that justice is equality, and so it is, though not for everybody but only for those who are equals; and it is thought that inequality is just, for so indeed it is, though not for everybody, but for those who are unequal" in https://www.loebclassics.com/view/aristotle-politics/1932/pb_LCL264.211.xml Politics, III. V. 8.
Misattributed
This first appears in 1974 in an explanation of Aristotle's politics in Time magazine, before being condensed to an epigram as "Aristotle's Axiom" in Peter's People (1979) by Laurence J. Peter
“Aristotle's axiom: The worst form of inequality is to try to make unequal things equal.”
Source: Peter's People and Their Marvelous Ideas

“There is nothing more unequal than the equal treatment of unequal people.”
Source: Putting systems to work (1992), p. 63 Cited in: Lars Skyttner (2005) General Systems Theory: Problems, Perspectives, Practice. p. 103

Expeditions of an Untimely Man, §48 Progress in my sense (Streifzüge eines Unzeitgemässen §48 Fortschritt in meinem Sinne). Chapter title also translated as: Skirmishes of an Untimely Man, Kaufmann/Hollingdale translation, and Raids of an Untimely Man, Richard Polt translation
Twilight of the Idols (1888)
Original: (de) Die Lehre von der Gleichheit! ... Aber es giebt gar kein giftigeres Gift: denn sie scheint von der Gerechtigkeit selbst gepredigt, während sie das Ende der Gerechtigkeit ist... "Den Gleichen Gleiches, den Ungleichen Ungleiches - das wäre die wahre Rede der Gerechtigkeit: und, was daraus folgt, Ungleiches niemals gleich machen."

Dissenting in New York v. United States, 331 U.S. 284, 353 (1947).
Judicial opinions

Source: Morals and Dogma of the Ancient and Accepted Scottish Rite of Freemasonry (1871), Ch. II : The Fellow-Craft, p. 44
Context: From the political point of view there is but a single principle,— the sovereignty of man over himself. This sovereignty of one's self over one's self is called Liberty. Where two or several of these sovereignties associate, the State begins. But in this association there is no abdication. Each sovereignty parts with a certain portion of itself to form the common right. That portion is the same for all. There is equal contribution by all to the joint sovereignty. This identity of concession which each makes to all, is Equality. The common right is nothing more or less than the protection of all, pouring its rays on each. This protection of each by all, is Fraternity.
Liberty is the summit, Equality the base. Equality is not all vegetation on a level, a society of big spears of grass and stunted oaks, a neighborhood of jealousies, emasculating each other. It is, civilly, all aptitudes having equal opportunity; politically, all votes having equal weight; religiously, all consciences having equal rights.