Who invented projective space $\mathbb{P}^n$ as an extension of the usual [affine space][1] $\mathbb{A}^n$?

Who was the first person to consider projective closure of
[plane affine algebraic curves][2] (curves in $\mathbb{A}^2$)? Was it the same person?


  [1]: http://en.wikipedia.org/wiki/Affine_space%20affine%20space
  [2]: http://en.wikipedia.org/wiki/Algebraic_curve%20plane%20affine%20algebraic%20curves