LOL!
The carved hillside figures dotted around Englands Chalk Downs have nowt to do with illegal toxins!
One - (at Westbury? I forget) - is modern, a symbolised version of the badge of the Army regiment whose home barracks is in the area.
Another of known history is that near Weymouth*, depicting King George III riding his horse Eastwards, so away from Weymouth. He visited the town fairly often, staying with a friend or a resident there but also for the new-fangled sea-bathing notion his doctors prescribed for his illness they genuinely could not understand or cure at the time. At least it gave him a break from the noisy and noisome, smoke-filled miasma of London; and did him no harm, unlike the enemas, emetics, blood-letting and ghastly concoctions that were contemporary medical stock-in-trade.
(Immersing oneself in the sea, though? Strange idea... Will it catch on?)
Other Chalk horses, and the Cerne Giant man - very definitely he is - are of unknown ages and purposes, though not for want of proper research by archaeologists. (As with stories woven around so many other Ancient Monuments, discount colourful speculation and invented "legends" by people unable to admit, "I do not know".)
So nothing to do with the sort of illicit rubbish you list, though perhaps some of the King's medication might have had more in common with them, than we think. Even if only by being potentially dangerous toxins of no conceivable benefit!
.......
*Strictly, he visited Melcombe, on the North side of the R. Wey estuary. Weymouth proper is on the South bank but similarly to so many other towns, its name became associated with the whole lot. Melcombe gained the Royal suffix 'Regis' from the King's patronising of the town, which made it something of a Place To Be.
