A collection of five letters written by Albert Einstein to fellow physicist Paul Hertz sold for $161,000 at Swann Auction Galleries' November 26 Autographs auction in New York.
The letters, penned between 1910 and 1915, reference his work on the theory of relativity - published in 1916.
The collection realised a 61% increase on a $100,000 estimate.
The letters invite Hertz to discuss his paper on thermodynamics as well as giving an insight into the problems Einstein was having in the development of relativity.
Einstein also criticises Hertz's proposition for a solution to what has become known as the "hole argument".
The auction record for a letter by Einstein remains �170,000 ($275,706), set in London in 2008.
Earlier this year, a bible inscribed by Einstein realised $68,500 at Bonhams New York.
Two handwritten pages from Mozart's score for the Serenade in D Major realised an identical figure of $161,000.
Written in Vienna in the summer of 1773, when the composer was aged just 17, the work is scored for two oboes/flutes, two horns, two trumpets and a solo violin.
It was most likely produced as a Finalmusik piece, which were traditionally composed for the end of year performances at Salzburg Benedictine University in Austria.
The working draft comprises bars 52-70 and features annotations in brown ink.
We have a piece of a score by legendary saxophonist John Coltrane, also featuring handwritten notations.
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