Rick has some good advice.
straight water would be your #1 choice for soaking
If the seed coat is thick and hard, you might want to scarify (small cut/scratch) and then soak in water
If that doesn't work, then try hydrogen peroxide(3%) in dilution recommendation
I have used straight 3% hydrogen peroxide for extremely hard seeds, but as Rick mentioned, there is a chance that choice may damage the seed.
Experiment with one seed and see what happens. If you choose to soak with H2O2, only soak for a few hours and/or until you seed the seed swell
Different seeds will have different results
Here's a very helpful link
http://www.using-hydrogen-pero...
