Quote by Nikola Tesla

If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search... I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.

Please suggest source details if you know: book, page, year, online article address (url), correction (different author...), etc.. Thanks.