Quiet Quentin (script) aids in searching Google Books for attesting quotations. To enable this gadget, tick "Quiet Quentin (QQ), a gadget assisting in finding citations (quotations)" in the Gadgets tab of your preferences (or in Wiktionary:Preferences/V2.)
How to use: click the "QQ" tab at the top of the page (or press Alt-Shift-9), put in your search terms and click the search button. A list of results will then show up: to select one for inclusion, click the "[pick]" link on the left of the result. When you are done, click the "Picked citations" tab; you will be presented with wikicode you can copy and paste into the edit window. After carefully checking the citations for errors (like misscans, wrong or incomplete metadata), emboldening the term and ensuring that it is presented in proper context, save the page.