The son of Daniel David Palmer, Bartlett Joshua Palmer was the leader of the “Universal Chiropractic Association”. BJ Palmer leased neurocalometers, devices which contained a thermocouple (a piece of electrical equipment that measures temperature).
It is hard to see how this device would be useful for detecting misalignments in the spine, or pinched nerves, given that it can apparently do no more than measure temperature or convert heat into electric power. Palmer nevertheless chose to lease these instruments for $2200 (the original price was $1150). His profit margin must have been huge, given that the devices cost $100 to build. Palmer apparently persuaded thousands to buy into this dubious device, thereby making a small fortune (in the 1920s, the price of a single neurocalometer, $2200, was itself a hefty sum of money).
Palmer was apparently paid $2200 per neurocalometer, and a further $10 per month for a ten year period. As a successful entrepeneur, he was quick to follow up this scheme with a similar one:
In 1935, eleven years after Palmer introduced the neurocalometer and about one year after the ten-year lease many chiropractors had on the device ran out, Palmer introduced the neurocalograph, which was essentially a neurocalometer that made an automatic graph of “nerve interference” as it was found. [Via chirotalk, which uses fairly strong language in discussion of the device.]
A 1993 Canadian chiropractic consensus conference concluded that paraspinal measurement with thermocouple devices “has not been shown to have good discriminability, and both their validity and reliability of measurement are highly doubtful.” Stephen Barrett thinks that this was a “politically correct” way of describing the device’s usefulness. Link.
Simon Singh and Edzard Ernst mention the neurocalometer in their excellent book Trick or Treatment.