I've eaten 10 whole seeds (1.5oz, grated) in one sitting, and yet I live. I was 240lbs at the time. I recommend never, ever taking that much! Nutmeg doesn't get much better at higher dosages, and you can be poisoned by it.
The high itself isn't too bad, but can get tense if you've taken too much. It's like getting really stoned on cannabis shade leaves, but with fewer visuals, IME.
And I'd like to point out that while nutmeg can produce some anticholinergic effects, it is in NO WAY comparable to diphenhydramine. I've taken a lot of diph. Diph will make you forget what you were doing 20 seconds ago. Diph makes you delirious. The dry mouth diph produces is sooo much worse.
Nutmeg, even at the dosages I took, never made me forget what I was doing. It did become scary, and I thought I might go into cardiac arrest or suffer some kind of CVA, but my memory was fully intact, and there was no delirium. At all. The dry mouth was entirely manageable, but my eyes... sooo red.
After a while you may learn to despise nutmeg's taste. If this happens, you can pour the grated seeds into cold milk and gulp it down quickly. It takes only a few seconds, and then it's done. The milk will mask the flavor a little, and will also help settle your stomach.
Another one of nutmegs effects: it makes your body feel minty.
