A love letter by Napoleon, words of comfort from John Donne and a plea for tolerance from Mahatma Gandhi are among the treasure of a private collection up for auction in London next month, Christie's auctioneers said Monday.

The extensive collection, estimated to sell for $4 million at the July 3 sale, was quietly amassed over three decades by the late Albin Schram, who kept them in a filing cabinet in his home in Lausanne, Switzerland, according to Christie's.

The letter from Napoleon to Josephine, given to Schram by a family member in 1973, was the inspiration for his extraordinary collection, Christie's said.

Schram pursued his new passion in auction rooms in London, Paris and Germany, usually bidding in person, said Thomas Venning, director of Christie's books and manuscripts department.

"Schram's guiding principle was his own insatiable intellectual curiosity, pursued through his voluminous reading," Venning wrote.

The collector's last wish-list in March 2005 included letters of Czech poet Jan Neruda, American poet Walt Whitman, U.S. President Richard Nixon and the 14th century Bohemian patriot Jan Zizka, Venning wrote.

Napoleon's letter, one of three to his future wife that are known to survive, was given to Schram in 1973 by a family member, Christie's said. Its sale price was estimated price at up to $100,000.

The letter was written after an argument about her family's wealth, leading to accusations that Napoleon did not love her for herself.

In the letter he declares his passion: "I send you three kisses one on your heart, one on your mouth and one on your eyes."

But the star of the collection is a letter by Donne, the celebrated priest and poet, which Christie's said is "the finest manuscript by his hand in existence" and is estimated to sell for $240,000).

Donne wrote to Lady Kingsmill in 1624, offering consolation for the death of her husband.

"Let us not, who know in God's house there are many mansions, but yet have no model, no design of the form of that building, wonder at his taking in of his materials, why he takes the young, and leaves the old, or why the sickly overlive those, that had better health," Donne wrote.

A letter from Gandhi, estimated to sell for up to $24,000, was written 19 days before his assassination and pleads for tolerance of Muslims.

A letter written in 1831 by Alexandr Pushkin, said to be only the second by his hand to appear at auction for more than 30 years, is estimated to sell for up to $160,000.

Pushkin wrote to Baron E. Rosen, editor of the almanac Altsiona, saying that he could not offer any short works for publication because he was busy preparing the third edition of his poems.

A letter from Isaac Newton (1643-1727), in which he compares his views on gravity and the universe to those of Plutarch, Aristotle and Plato, was estimated to fetch up to $100,000.

Schram, who died in 2005, was born in Prague in 1926 to Austrian parents, Christie's said.

He was drafted into the German army in World War II and taken prisoner late in the conflict and confined at Kaliningrad in Russia. He escaped in mid-1945 and made his way back to Austria.