AR(R)OW: "W" Reference

[ScubaPilot77]

In the States most of us learned the acronym "ARROW" for required documents on board a civil aricraft:
Airworthiness certificate
Registration
Radio station license (if operated internationally)
Operating limitations (placards and flight manual)
Weight and balance

The first four requirements are covered under 14 CFR Part 91.203 and 91.9. Can anyone point to the specific FAR which requires the weight and balance to be on board?

Thanks.