Christie's will offer for sale a drawing by Renaissance master Raphael which he used as a study for a figure in a Vatican fresco, and expects it to break the record for an old master drawing sold at auction. “Head of a Muse” will go under the hammer at the London sale of old masters and 19th century art on Dec. 8 and has been estimated at 12-16 million pounds ($20-26 million). The Raphael drawing was a study for a figure in “Parnassus”, one of a series of four frescoes in the Stanza della Segnatura in the Vatican commissioned by Pope Julius II and executed between 1508 and 1511. Christie's said the series was “widely considered to be the artist's greatest masterpiece.”