Synesthesia

There are of course the eyes that are smiling and mouths that are dreaming. By chance today I came across this one:

As an imperfect actor on the stage
Who with his fear is put besides the part,
Or some fierce thing replete with too much rage,
Whose strength's abundance weakens his own heart;
So I, for fear of trust, forget to say
The perfect ceremony of love's rite,
And in mine own love's strength seem to decay,
O'ercharged with burthen of mine own love's might.
O, let my looks be then the eloquence
And dumb presagers of my speaking breast;
Who plead for love, and look for recompense,
More than that tongue that more hath more express'd
O, learn to read what silent love has writ!
To hear with eyes belongs to love's fine wit.

William Shakespeare, Sonnet 23