Core rope memory
From Just Solve the File Format Problem
Core rope memory was a form of Read Only Memory (ROM) used in the early days of computing, based on use of ferrite cores as transformers. It had a higher capacity than the read-write core memory used in those days, 72 kilobytes per cubic foot. Data was woven in by hand, generally by female workers. The Apollo Guidance Computer used this sort of memory to store its programs.
