The Vicksburg Campaign, Vol. 2, Grant Strikes a Fatal Blow,
Edwin Bearss, pp. 562/3
"Soon after daybreak, on the 14th, Pemberton prepared to shift his headquarters from Bovina to Edwards. As Pemberton and his staff were swinging into their saddles, they were hailed by Capt. William S. Yerger. Riding up on a sweat-lathered horse, Yerger handed Pemberton an important dispatch from General Johnston.
"This message was made out in triplicate and handed to Captain Yerger and two other couriers. One of these was a Northern agent who, on the 14th, delivered his copy of Johnston's dispatch to General McPherson.*
"*To avoid McPherson's patrols, the courier, on his journey from Jackson to Bovina, had detoured to the north of Clinton."
Note: Bearss does not source the above.
Pemberton's reply is found in the OR I, Vol. 24, Part 3, p. 877.