The number is unlimited.
The Romans made organs which must have been simple from the musical standpoint, though they were complicated in their mechanical construction.

They were called hydraulic organs.

The employment of water in a wind instrument has greatly perplexed the commentators.
Cavaille-Coll studied the question and solved the problem by demonstrating that the water compressed the air.

This system was ingenious but imperfect, since it was applicable only to the most primitive instruments.

The keys, it seems, were very large, and were struck by blows of the fist.
Let us leave erudition for art and primitive for perfected instruments.
By the time of Sebastian Bach and Rameau the organ had taken on its grandiose character.