This was a serendipitous discovery. I was reading Nathaniel Hawthorne's Tales from Province House when I happened upon this line near the beginning:
At my entrance, an elderly person was smacking his lips with a zest which satisfied me that the cellars of Province House still hold good liquor, though doubtless of other vintages than were quaffed by the old governors. After sipping a glass of port sangaree, prepared by the skillful hands of Mr Thomas Waite, I besought that worthy successor and representative of so many historic personages to conduct me over their time-honored mansion.
Thus opens a series of four macabre short stories set in the Province House, the old home of the governors of the Massachusetts Bay Colony. It was built in 1679 and was occupied, first by governors and later as an inn or for other uses until 1864, and finally demolished in 1922. For more on the real history of the Province House, see the Wikipedia entry but I daresay Mr Hawthorne's tales are more fun. They can be found in his famous book Twice-Told Tales.
Upon hearing of this antique libation, I had to try it. It took only a little archeology to discover that, like Hawthorne's Old Esther Dudley of the Province House, it belongs to an old, established, and now largely forgotten family: the sangarees are typically served iced, in a tall glass filled with crushed ice, comprising some spirit, a little simple syrup, and soda almost to fill the glass. In most versions, a small amount of tawny port is floated on the surface, followed by a sprinkling of nutmeg. Mr Hawthorne's Port Wine Sangaree, being already of port, would have had brandy floated on top, accompanied by the nutmeg so popular in colonial days.