What are some bicycles of/for the mind

Had to look this up.

It's a quote from Steve Jobs saying he thought computers would enhance minds the way bicycles enhance efficiency of travel.

(One of the search results.)

Books about history, philosophy, and science.

Memory training tools. Like the memory palace, the person-action-object method, acronyms and mnemonics.

Visualisations like using the abacus method to do fast and accurate arithmetic.

And human-executable techniques like the doomsday algorithm and George Marsaglia's random number generator.