What did Lincoln say to Sherman at City Point?

As they so often do, The Edge of the American West has good background on an important historic event that took place on this date. The essay begins:

On this day in 1865, Abraham Lincoln returned to Washington from a trip to Virginia, where he had visited Grant’s headquarters, surveyed Richmond in captivity and sat in Jefferson Davis’s chair, contemplating the imminent end of war.

Arriving back in the capital, Lincoln stopped first by the house of William Seward, his Secretary of State, who was laid up owing to a carriage accident that left him with a broken arm and jaw. The president proposed a national day of thanksgiving, and held his face close to Seward’s to hear his colleague’s answer. Seward counseled, not yet. Sherman had still to secure the surrender of Joseph Johnston. Until then the Confederacy remained unconquered.

Lincoln would not live to see the end Seward advised him to await. But when that conclusion came, Lincoln’s trip to Virginia would hang heavy over it.