I haven't tried..
But most USB powered hdd draw about 950ma -1000ma (1amp) so if your going to try it you will need a decent power supply preferably above 2.5 amp also you would need to edit your config.txt to include this line.
The above sets the current output on the pi to 1amp rather then the default 600ma
This isn't something I would recommend or even guarantee it will work. The safest way would be to buy a USB powered hub and directly connect external Hdd into that.