On New Year's Day I was hiking in Marin County (near Fairfax, off Bolinas Road) and picked up some nuts that looked like chestnuts. They were bitter to taste, so I brought them home and baked them in the oven for a while. Now they have a more mellow taste, though I am still finding them somewhat bitter. Seems like there is lots of natural oils in these nuts. I did a little research before I began chewing (just to make sure I wouldn't poison myself). I found a wikipedia entry but not much else. I thought they were Japanese chestnuts. Then I asked a friend and he said they are california buckeye, a seed that is considered poisonous. Wooops!
Next time, I'll try to leach them first, like the Indians did, to remove the toxins.