The panoramic plate on the Beacon gives a tale about the cairns.....“Legend has it the Giant Bolster could stand with one foot on St.Agnes Beacon and the other on Carn Brae. Giant Bolster’s wife was made to clear the neighbouring field of stones, three aprons full are seen today as barrows (burial mounds) on top of the beacon”.
I’ve also read that the two giants on St.Agnes Beacon and Carn Brea would hurl bolders across the space between the two hills, and Bolster was able to stride from the Beacon to Carn Brea with one mighty step.