"extracting Sun-Beams out of Cucumbers"
GNU Free Documentation LicenseCucumbers - Credit: Piotrus
This phrase has come to symbolize the epitome of useless projects, thanks to this mention in Gulliver's Travels.

In Princess Ida, a century and a half later, William Schwenck Gilbert (1836 - 1911)satirized women's education, he can think of nothing better to symbolize the folly of women trying to use their brains. He says:

"And weasels at their slumbers

                                                      They treplan--they treplan

                                                      To get sunbeams from cucumbers

                                                      They've a plan -- they've a plan"

However, the last laugh is on Swift and on Gilbert. In the modern world, energy is derived from plant life in an ever-increasing level. And women have proven themselves more than capable of using their brains.