What does this poem by William Butler Yeats mean?

[Play-doh Man]

Had I the heavens' embroidered cloths,

Enwrought with golden and silver light,

The blue and the dim and the dark cloths

Of night and light and the half-light,

I would spread the cloths under your feet:

But I, being poor, have only my dreams;

I have spread my dreams under your feet;

Tread softly because you tread on my dreams.