A Midsummer Night's Dream, IV, ii

THESEUS: The lunatic, the lover and the poet
Are of imagination all compact:
One sees more devils than vast hell can hold,
That is, the madman: the lover, all as frantic,
Sees Helen's beauty in a brow of Egypt.

A Midsummer Night's Dream, V, i

THESEUS: The poet's eye, in fine frenzy rolling,
Doth glance from heaven to earth, from earth to heaven;
And as imagination bodies forth
The forms of things unknown, the poet's pen
Turns them to shapes and gives to airy nothing
A local habitation and a name.

William Shakespeare, 1564-1616