What does this line of Isaac Newton's rap video mean?

[Jamin2112]

Go to 1:24 of this video:

He recalls some integral he wrote at a young age:

" ... times the sixty-fourth power of ... what?" and looks confused. At 1:44 Neil Degrasse Tyson says, "By the way, the answer to your little calculation is i."

Can someone explain the historical reference to me? Was there some integral that Sir Isaac Newton could never solve?

 

[Vagn]

The integral sec y dy from zero to one-sixth of pi is log to base e of the square root of three times the sixty-fourth power of what?!

(While the concept of imaginary numbers and i existed during Newton's time, he and other great thinkers of the time (such as René Descartes, that later solved the equation with "Descartes' i") dismissed the idea of imaginary numbers as fanciful. Thus, despite his best powers of deduction, Newton was stymied by the equation he wrote and thought it unsolvable.)

This also comes from a calculus limerick which reads similar to Newton's line:

"The integral sec y dy (pronounced "seek y dee y'")
From zero to one-sixth of pi
Is log to base e
Of the square root of three
Times the 64th power of i"

http://epicrapbattlesofhistory.wikia.com/wiki/Sir_Isaac_Newton_vs_Bill_Nye/Rap_Meanings

 

[Jamin2112]

http://epicrapbattlesofhistory.wikia.com/wiki/Sir_Isaac_Newton_vs_Bill_Nye/Rap_Meanings

By the way, I wasn't too lazy to Google this question. I asked here because I didn't think there would be an entire wiki devoted to the Youtube video.

 

[Joey42]

I have the book in which this is written in but I can't find what section