Definition of "tranquilly"

When we see a party looking tranquilly up to heaven, unconscious that his body is shot through and through with arrows, we know that that is St. Sebastian.

1869, Mark Twain [pseudonym; Samuel Langhorne Clemens], “LEARNING THE RUDIMENTS”, in The Innocents Abroad, or The New Pilgrims’ Progress; […], Hartford, Conn.: American Publishing Company. […], page 238