Not much, to judge from the former Treasury secretary’s new book, Stress Test: Reflections on Financial Crises.

Via Politico’s Playbook:

“Dealing with Congress, to put it mildly, did not feel like a careful, deliberative journey in search of the best public policy. I remember going to meet the personable Senator Brown [R-Mass., now running for Senate in N.H.], who had recently arrived in Washington after a campaign spent attacking the ‘Cornhusker Kickback’ … We talked about our kids and about triathlons.

“When the conversation finally turned to substance, he said he liked the idea of financial reform and expected to be with us. But without any irony or self-consciousness, he said he needed to protect two financial institutions in Massachusetts from the Volcker Rule’s restrictions. Then he furrowed his brow and turned to his aide. ‘Which ones are they, again?’ he asked.” (p. 421)

In Tuesday’s Boston Globe, Matt Viser provided the answer.

The companies, Brown’s aide said, were Fidelity and State Street.

Viser’s piece also details Geithner’s fraught dealings with Brown’s polar opposite, Massachusetts Sen. Elizabeth Warren (D-Ragged Edge of the Middle Class).

Geithner and Warren had strongly diverging viewpoints of Wall Street regulation, which caused disagreements and heated discussions. Or, as Geithner wrote, “I had a complicated relationship with Warren.”

Neither Brown nor Warren responded to the Globe’s request for comment.

Huh. Silence may be golden, but it won’t pay the rent for either of those turtles.