use a nail file and gently file one side of the seed. but do it gently, and only for like 30-60 seconds, then soak it until it sinks, whether its 2hours or 24 hours, then put use the paper towel method...
some seeds need to go thru conditioning to awaken them from whats called the seeds "dormancy"..some seeds need to be put in the freezer overnight before germination to act like the winter period the seeds would go thru if they were in the wild, some needs to be scratched *VERY GENTLY* with a small needle to allow the seed to soak water.