[iguy]

You can read the original description of the apparatus here:

http://galton.org/bib/JournalItem.aspx_action=view_id=180

It's a pendulum which is released (either silently or with a click), and a button for the subject which records the angle at which it was pressed.

[hymen0ptera]

It doesn't sound like they actually compared apples to apples by performing the same test as a modern replication of results though.

A similar apparatus is not named or sited, when noting the modern equivalent. Does that matter? Couldn't there be side-effects for measure reation time to different stimuli?

Also, did modern 1941 measurements operate with the benefit of newer advancements, such as high-speed cinematography to produce objective slow-motion footage?