Don’t try this at home, kids.
Aubrey “heard the minister of Aubury say those huge stones may be broken in what part of them you please without any great trouble. The manner is thus: they make a fire on that line of the stone where they would have it to crack; and, after the stone is well heated, draw over a line with cold water, and immediately give a smart knock with a smyth’s sledge, and it will breake like the collets at the glasse-house.”
(quoted in ‘Avebury, the biography of a landscape’ by Pollard and Reynolds (2002), maybe from Aubrey’s ‘Monumenta Britannica’?)