And even though there is a Belgian band (MekanOrganiK) that has an album named "How to extract sunlight from Cucumbers" -
I believe your reference has to do with the novel "Gulliver's Travels".
In Gulliver's Travels, Swift's satirical treatment of contemporary science, particularly as focused in the section dealing with the Grand Academy of Lagado, reached great new heights. (On one day in 1710, Swift visited Gresham College, the Tower, a puppet show and Bedlam. How his imagination must have responded …)--Extracting sunlightThe first man I saw was of a meagre aspect, with sooty hands and face, his hair and beard long, ragged, and singed in several places. His clothes, shirt, and skin, were all of the same colour. He has been eight years upon a project for extracting sunbeams out of cucumbers, which were to be put in phials hermetically sealed, and let out to warm the air in raw inclement summers. He told me, he did not doubt, that, in eight years more, he should be able to supply the governor's gardens with sunshine, at a reasonable rate: but he complained that his stock was low, and entreated me "to give him something as an encouragement to ingenuity, especially since this had been a very dear season for cucumbers." I made him a small present, for my lord had furnished me with money on purpose, because he knew their practice of begging from all who go to see them. (III.v)