It's HF market wizards, chapter 5. I recently re-read this.
For me the most interesting part of this story is that he is probably more secretive than anyone else in the book about what he does, and I found the description of what he did pretty intruging. So he's doing some kind of non linear analysis, or linear analysis on derivations of observable data like price, but on effects that work across markets, and also on effects that have persisted for some kind.
So quite different from the normal data mining approach I'm so skeptical about.
By the way I'm not sure what "a hundred thousand dollars worth" of data actually means, or meant in the past. Nowadays you could get that data for free. The normal model for getting data is a subscription model, which means you might be paying up to $500K a month to get tick level data from every exchange in the world, but the value of that data is hard to quantify.
GAT