Museum Boerhaave – Plate on a pump used to make ultra-low temperature

Kamerlingh Onnes made helium into a liquid by cooling it close to 0 Kelvin. He used several pumps in series, using the same principle as the household fridge.

From their website:

National Museum of the History of Science and Medicine

As the national treasury of scientific endeavours, the museum shows some 400 years of advances in knowledge. Developments in the various sciences can be viewed in 24 rooms on two levels. The emphasis is on contributions from the Netherlands.