WHAT if I bade you leave
The cavern of the mind?
There's better exercise
In the sunlight and wind.
I never bade you go
To Moscow or to Rome.
Renounce that drudgery,
Call the Muses home.
Seek those images
That constitute the wild,
The lion and the virgin,
The harlot and the child
Find in middle air
An eagle on the wing,
Recognise the five
That make the Muses sing.

William Butler Yeats

http://www.poemhunter.com/poem/those-images/