Sirce Luckwielder (paraphrased)
In the flashback [of Words of Radiance] with Shallan meeting Hoid, Hoid pours something from a pouch into his cup and drinks it. Are these Allomantic metal shavings?
Brandon Sanderson (paraphrased)
His answer was that there was something indeed significant about what Hoid placed in the cup, but that it was not necessarily Allomantic shavings. He wouldn't tell me what it specifically was and gave me a R.A.F.O. card.