A sketchbook of the British poet and artist William Blake that sold 125 years ago for the equivalent of $30 is expected to fetch about $875,000 next month.

"The works of William Blake have been in such demand for so long that it is rare for anything by him to come to market now," Anthony Browne, head of English watercolors and drawings at Christie's, said Friday. The auction is in London on March 21.The sketchbook sold for about $30 at Christie's sale of the studio of Victorian artist William Mulready in 1864. The auction house estimate now is about $875,000.

Blake, who died in 1827, earned a meager living as an engraver while writing and publishing poems on biblical and mythological subjects illustrated with his own colored engravings.