Actually until industrial revolution the only asset generating yield was not gold but landowning. It wasn't risk less but on average it was the only asset available generating positive returns.

The castles and gold vaults were nice but only as a temporary store of wealth. Most of rulers were constantly in debt used to pay for wars and representation (buying influence).

XIX century introduced bonds which paid yields in coin, bankrupted most of landowners and created this new breed of entrepreneur capitalist.