It is interesting that Rogers Mushrooms gives the taste of many of the species described, including some poisonous ones, with the statement that provided you only taste with the tip of your tongue and then give your mouth a good rinse afterwards, you should suffer no ill effects. I'm assuming that this is a reliable source and that the statement is therefore true...
...however, I'm not sure that I would want to taste a potentially deadly species. For example, if we take perhaps the worst case example, I wonder how much Death Cap you would need to eat to become ill (or more specifically how little you could eat and not become ill) - i.e. could you taste Death Cap using the tip-of-the-tongue method as described in Rogers Mushrooms and survive? Not that I'm going to try it myself...
Geoff
You need to swallow a teaspoonful to reliably do yourself in. I don't routinely taste wild mushrooms, only certain groups like milk caps and russulas. I know that deathcaps are tasteless, but that is taking the word of good field field guides like rogers and I am no hurry to try out tasting death caps. However horses hoof has no known toxicity and I would be quite happy to put a small piece of it in my mouth,as I am pretty sure no harm would come of it. I don't wash hands after handling it, in fact i don't wash my hands after handling death caps either. As the amount of fungi that remains on hands after handling is so small it would so far below what is required to cause poisoning, so there is no risk.
Some wild plants and the odd fungi can leave a bitter taste on hands after handling, I would wipe my hands after handling if this is the case. After tasting some fungi the bitter taste can be quite persistent indeed. The other week a tasted a russula drimeia (sardonia), it was the worst tasting thing have ever had in my mouth, so bad that water couldn't get rid of the taste, so I took a unripe blackberry and ate that, that actually worked. If anything out there causes that type of problem a sharp taste like sorrel, dock rowan or unripe edible fruit normally fixes it for me.
Horse hoof shouldn't cause any problems from handling. Don't handle any unknown member of the carrot family without washing you hands though, they can cause very nasty rashes indeed, and some are very toxic if ingested.