Roman political equilibrium

From Polybius' The Histories, 146 B.C.E, Book 6, Paragraph 10:

[I]n each constitution there is naturally engendered a particular vice inseparable from it: in kingship it is absolutism; in aristocracy it is oligarchy; in democracy lawless ferocity and violence; and to these vicious states all these forms of government are, as I have lately shown, inevitably transformed. Lycurgus, I say, saw all this and accordingly combined together all the excellences and distinctive features of the best constitutions, that no part should become unduly predominant and be perverted into its kindred vice; and that, each power being checked by the others, no one part should turn the scale or decisively out-balance the others; but that, by being accurately adjusted and in exact equilibrium, the whole might remain long steady like a ship sailing close to the wind.