It doesn't look much like the mind of a genius. There are revisions, crossings out and corrections.

Yes, even the great Albert Einstein got his sums wrong. His agonising moments of indecision while he figured out the world's most famous mathematical equation were revealed for the first time yesterday.

Now 80 years later his original working document is expected to be sold for 4 million pounds sterling. It is the most detailed review of his Theory of Relativity and represents 55,000 pounds sterling a page.

Einstein's theory laid the foundations for 20th century science - it led to the physics of splitting the atom, the origins of nuclear power and the theoretical line of thought which produced the first atom bomb.

Perhaps the simplest explanation came from Einstein himself as he once tried to get his theory across to a secretary.

He said: "If you spend an hour with a pretty woman it feels like a minute. If you spend a minute sitting on a hot stove it feels like an hour."

Einstein died in April 1955 aged 75. His 72-page unpublished manuscript from 1912 went on show at Sotherby's in London yesterday. It is due to go under the hammer at Sotherby's New York auction rooms on March 16.

The document, which begins in pencil, switches to brown ink and then to black ink, provides a fascinating insight into Einstein's mind. It is very much a working document - every page shows extensive reworking and redrafting, with whole paragraphs and equations crossed out. It is full of previously unavailable revelations about Einstein's thinking at this crucial point in his career.

The rarity value of the manuscript is further enhanced by the fact that despite his brillience, Einstein was very casual about keeping his papers. David Redden, senior vice-president in charge of Sotherby's books and manuscritps department, said yesterday: "It is the most important manuscript in private hands in the world." His original idea L = MC squared was changed to E = MC squared after much wracking of Einstein's brain.

His decision to cross out the letter L and replace it with E the manuscript appears on the front cover of Sotherby's catalogue. The document made auction history in December 1987 when it fetched 780,000 pounds sterling at Sotherby's and set a record for any manuscript sold in America. Now it is set to change hands again.

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