In Spenser's poem Prothalamion, he dreams about the beautiful Leda and her swan lover. Spenser lived from 1522 - 1599. Below is the third section of the poem, which in general talks about a beautiful day along the Thames river and the sights he sees there.

With that I saw two Swannes of goodly hewe
Come softly swimming downe along the Lee;
Two fairer Birds I yet did never see;
The snow, which doth the top of Pindus strew,
Did never whiter shew;
Nor Jove himselfe, when he a Swan would be,
For love of Leda, whiter did appeare;
Yet Leda was (they say) as white as he,
Yet not so white as these, nor nothing neare;
So purely white they were,
That even the gentle streame, the which them bare,
Seem'd foule to them, and bad his billowes spare
To wet their silken feathers, least they might
Soyle their fayre plumes with water not so fayre,
And marre their beauties bright,
That shone as heavens light,
Against their Brydale day, which was not long:
Sweete Themmes! runne softly, till I end my Song.

Swan Lake - a History
Swans - the Children of Lir

Leda and the Swan - History
Leda and the Swan - WB Yeats Poem