I have some plain Witch Hazel and I was thinking of adding some menthol to it. What would be the best route to do this? Could something like Menthol Crystals (http://cgi.ebay.com/2-OZ-Menthol-Cr...814?pt=LH_DefaultDomain_0&hash=item45f0fd22ee) just be added to Witch Hazel?