I did this a bit later in the game, but you can do this at the very beginning if you choose too. Use the coffin as a ramp, time the jump at the bottom of the coffin to launch onto the ledge. From there get to the carriage, turn around and you want to time + angle your jump so you land on the other side of the fence's ledge but not fall off. Once on the other side, all the goodies, such as the Cainhurst Summons, Communion Rune, are yours. You can also skip several bosses and go straight into the Forbidden Woods
