コーネルの箱

http://images.google.com/images?hl=ja&lr=lang_ja&ie=UTF-8&oe=UTF-8&q=%E3%82%B3%E3%83%BC%E3%83%8D%E3%83%AB%E3%81%AE%E7%AE%B1&num=50&um=1&sa=N&tab=wi

http://images.google.com/images?um=1&hl=ja&lr=lang_ja&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=cornell+box&spell=1