In general, the best way to achieve very-high pressures is  to squeeze the sample with something hard.

The Paris-Edinburgh cell doesn't use menhirs but works on a similar principal. The sample in placed between two hard anvils made from either tungsten-carbide or sintered industrial diamond.

Because we don't have Obelix, we use a hydraulic ram to apply the pressure. The Paris-Edinburgh cell's hydraulic ram is a key breakthrough. It has been very carefully designed to minimise both size and weight. The result is a ram with a 200 tonne capacity ( enough to lift two railway locomotives) which weighs only 50 kilogrammes and fits into a 30 cm cube.