Tracking down the Robert Frost references

At the start of the year I posted about Chief Justice Roberts's year-end judiciary report on the judicial adoption of new technology. My last paragraph was this:

[N.B., in the course of discussing the decline of the pneumatic tube system, the report also contains the line "But not even things gray can stay …" That sounded to me like a literary allusion of some kind, but Google didn't immediately return an obvious source. Is it an allusion to Robert Frost's Nothing Gold Can Stay?]

Where I merely had the energy to ask the question, Adam White actually dug in and found the answer - yes, it's Robert Frost. As White explains in the Weekly Standard:

It's not Roberts's first reference to Frost-far from it. He famously quoted Frost in the court's farewell letter to the retiring Justice Souter: "We understand your desire to trade white marble for White Mountains, and return to your land 'of easy wind and downy flake.'" (Souter replied in kind, quoting Frost's "Two Tramps in Mud Time.")

Indeed, this is not even the first of Roberts's year-end reports to quote Frost. He closed his 2006 report with a word of thanks to judges, judicial staff, and their families: "As Robert Frost reminded us - 'from the heart,' we work as one, whether -"together or apart."

The rest of the piece is full of excerpts of Roberts on Frost, and therefore worth reading.