Sophomore midfielder Adam McGowan closed out the first half's scoring on a sparkling offensive rush keyed when senior longstick Ethan Oberman picked up a ground ball in the midfield.
Oberman flipped the ball ahead to McGowan, who broke down the middle of the field uncontested and zipped a shot past Cirri for the 4-1 advantage.
Harvard outshot the Eagles 14-3 in the second period.
At times, Cirri was the lone force keeping the Eagles involved, as he made several quality saves, including stoning Buttles from point-blank range in the second.
Cirri made 22 saves but saw his robust GAA increase to 11:00.
Out of the intermission, the Crimson was aggressive and scored four times in the third quarter, seemingly at will.
The scoring included the first goal of the season from junior attackman Lawson DeVries.
DeVries was a key underclassman scorer for the Crimson last season, nailing down 20 goals and 11 assists while compiling a .445 shooting percentage.
But it was Sprong who wrote the final chapter of the victory, getting the Crimson's final three goals after Buttles had opened the lead to 9-3.
Harvard was typically effective clearing the ball, making 28 good out of 35, including 12 of 15 in the second half.
Notes
Harvard will have a busy spring break, hosting No. 14 Penn on Saturday before challenging No. 2 Duke on April 3 in New Canaan, Conn. The 6-0 Blue Devils boast the highest ranking in program history and have beaten three ranked teams in Maryland, UMBC and Navy.
With four goals, Sprong maintains the team scoring lead with nine goals and 10 points.
In just three games, Sprong has now equaled his goal total from his rookie season, when he scored nine goals and collected four assists.
Oberman collected his first point of the season when he assisted on McGowan's goal in the second.
HARVARD, 12-6 at Ohiri Field BC 1 0 2 3 - 6 Harvard 1 3 4 4 - 12
G:BC-Adair (3), Jewell (2), Finn (1); Harvard-Sprong (4), Buttles (2), Callan (2), DeVries (1), Watson (1), Leary (1), McGowan (1). A: BC-Cavanaugh (1); Harvard-DeVries (3), Watson (2), Buttles (1), Callan (1), Leary (1), Oberman (1), Christian (1), S: BC-Cirri 22; Harvard-Cynar 16.