Head of a Muse by Raphael was expected to fetch up to £16m
A record-breaking auction in London saw two works of art, a Rembrandt and a Raphael, sell for almost £50m.
The drawing by Raphael, Head of a Muse, sold for £29.2m, a world record price for any work on paper to go under the hammer, Christie's said.
It was also a world record price for the artist.
The Rembrandt painting, entitled Portrait of a Man, Half-Length, With His Arms Akimbo, fetched £20.2m, a record price for the artist at auction.
Christie's Old Masters and 19th-century art sale on Tuesday night fetched a total of £68,380,250 from 28 lots sold.
The auction house said it was the highest total for an auction of Old Masters.
'Glimpse into genius'
Raphael's Head of a Muse was drawn as a study for a figure in Parnassus, one of the series of four frescoes in the Stanza della Segnatura in the Vatican which was commissioned by Pope Julius II and which was executed between 1508 and 1511.
The drawing, which was offered at public auction for the first time in more than 150 years, had been expected to sell for £12m to £16m.
It was bought by an anonymous client on the telephone.
The previous record price for a work on paper was Danseuse au repos, a pastel by Edgar Degas, which sold in New York in November last year for US dollars 37,042,500.
Rembrandt's painting had not been seen in public for 40 years
Benjamin Peronnet, from Christie's, said: "Raphael is universally recognised as one of the greatest artists in history, and we are extremely excited to have sold a beautiful drawing by his hand which played a major part in the execution of one of the masterpieces of European art.
"This truly exceptional drawing offers us a glimpse into the working mind of a genius.
"The drawing is not only a work of genius in its own right but is also related to one of the artist's great frescoes in the Vatican and has come down to us in remarkable condition."
Rembrandt's painting went under the hammer for the first time since 1930, when it sold for £18,500 - a noteworthy sum at the time.
Before the pre-sale exhibition the late portrait had not been publicly displayed for 40 years.
It was also bought by an anonymous client bidding by telephone.
The previous world record price for a work by Rembrandt sold at auction was £19.8m.
Portrait of a Lady Aged 62 was sold at Christie's in London in December 2000.
Portrait of a Man, Half-length, With His Arms Akimbo, was painted in 1658 during one of Rembrandt's most artistically inventive periods.
It depicts an unknown sitter facing the artist with a defiant pose and hands on hips.