Magna Britannia
Magna Britannia was issued in 92 parts (1 shilling each), from January 1713/14 to April 1731, with Essex in parts 15 & 16, published Feb 1716/17 and March 1717. Despite the name, only English counties were covered.
Essex then also appears in volume 1 (of 6) covering the first 16 parts (11 counties), published in 1720.
There is a triangular distance table at the end of each county; the data is taken from the sequence of Garrett / Von Langeren / Simmons triangular tables, with the ultimate source being Norden's table in 1625.