The quote My so potent art comes from Prospero's speech in Act V, Scene I of The Tempest. I think is awesome that he got to actually give the line that is the name of the festival!
Ye elves of hills, brooks, standing lakes and groves,
And ye that on the sands with printless foot
Do chase the ebbing Neptune and do fly him
When he comes back; you demi-puppets that
By moonshine do the green sour ringlets make,
Whereof the ewe not bites, and you whose pastime
Is to make midnight mushrooms, that rejoice
To hear the solemn curfew; by whose aid,
Weak masters though ye be, I have bedimm'd
The noontide sun, call'd forth the mutinous winds,
And 'twixt the green sea and the azured vault
Set roaring war: to the dread rattling thunder
Have I given fire and rifted Jove's stout oak
With his own bolt; the strong-based promontory
Have I made shake and by the spurs pluck'd up
The pine and cedar: graves at my command
Have waked their sleepers, oped, and let 'em forth
By my so potent art. But this rough magic
I here abjure, and, when I have required
Some heavenly music, which even now I do,
To work mine end upon their senses that
This airy charm is for, I'll break my staff,
Bury it certain fathoms in the earth,
And deeper than did ever plummet sound
I'll drown my book.
And ye that on the sands with printless foot
Do chase the ebbing Neptune and do fly him
When he comes back; you demi-puppets that
By moonshine do the green sour ringlets make,
Whereof the ewe not bites, and you whose pastime
Is to make midnight mushrooms, that rejoice
To hear the solemn curfew; by whose aid,
Weak masters though ye be, I have bedimm'd
The noontide sun, call'd forth the mutinous winds,
And 'twixt the green sea and the azured vault
Set roaring war: to the dread rattling thunder
Have I given fire and rifted Jove's stout oak
With his own bolt; the strong-based promontory
Have I made shake and by the spurs pluck'd up
The pine and cedar: graves at my command
Have waked their sleepers, oped, and let 'em forth
By my so potent art. But this rough magic
I here abjure, and, when I have required
Some heavenly music, which even now I do,
To work mine end upon their senses that
This airy charm is for, I'll break my staff,
Bury it certain fathoms in the earth,
And deeper than did ever plummet sound
I'll drown my book.