[AT] O.T. Scribing on nearly flat rocks?

[Herbert Metz]

Off Topic
Need to scribe/write a plant name/couple words/etc on some nearly flat rocks to identify a plant, etc.
Letters/numbers must be readily legible from >six feet;   flat rock would lay on ground in front of a plant/row.
Expect only a couple rocks with same wording,  so would be more of a onesy-twosy situation.
Do not need the accuracy (or cost) of a pantograph.
We have a hand held electric vibrator with a sharp metal point,  but the narrow line is not readily visible from six feet.
We have a sizeable air compressor;  what about a needle scaler;  Harbor Freight has one on sale for $45?
Your opinions would be appreciated.
Herb