The MONIAC (a.k.a. the financephalograph) was an hydraulic computer, designed and built by engineer-turned-economist Bill Phillips in 1949.

Every home should have one!

Made of standardised items (pumps, tubes, valves, buckets), which can be mounted in a grid framework and plugged together. Sure, you can build Systems Dynamics models online at insightmaker.com, but where's the element of family fun? splashing water, whirring pumps, kinaesthetic joy.
-- sofacrat, May 20 2015

MONIAC on wikipedia http://en.wikipedia...iki/MONIAC_Computer
Invented by a New Zealander (of course) [sofacrat, May 20 2015]

MONIAC on YouTube https://www.youtube...watch?v=FeFwyWcIHts
Reserve Bank of NZ has a working model [sofacrat, May 20 2015]

random, halfbakery