NICHOLAS I, Emperor of Russia (1796-1855). Autograph letter signed ("Nicolas"), in French, to an unnamed Royal Highness. St. Petersburg, 8 April 1820. 2 pages, 4to, creased, a few inkstains. Thanking the recipient for her gracious reception of his son, who felt like a member of the family due to the warm hospitality. In a postscript, he asks to be warmly remembered to her daughter. Nicholas I manuscript material is rare on the market at auction.