In 1919, during a session of Sovnarkom, Lenin wrote a note and passed it to Dzerzhinsky: "How many dangerous counter-revolutionaries do we have in prison?" Dzerzhinsky scribbled, "About 1,500" and returned the note. Lenin looked at it, placed the sign of a cross by the figure, and gave it back to the Cheka boss. That night, 1,500 Moscow prisoners were shot on Dzerzhinsky's orders. This turned out to be a dreadful mistake. Lenin had not ordered the execution at all: he always placed a cross by anything he had read to signify that he had done so and taken it into account.
-- Orlando Figes, A People's Tragedy: The Russian Revolution 1891-1924.