An answer on this question on the cross validated stack exchange compared statistical power to a microscope, such that "in order to see small things you need a powerful microscope" is analogous to "in order to detect small effects you need high statistical power." I have heard this before from a colleague and I have also used it elsewhere as a pedagogical device to much benefit.
Is there a primary source for this metaphor? Who came up with it first? Or is it just a meme whose creator is now a meme (pending answers to this question)?