It seems to be alerting people to the danger of heavy stone ornaments overcoming their innate inertia to convert their potential energy into kinetic energy by suddenly becoming mobile and “leaping” from pedestals and other high places onto unwary bypassers.
The full sign is shown below — please double left click on the image to enlarge.
“Heavy stone ornaments can be unstable” is not really what one might call good news is it? One would kind-of expect the heaviness to play a better part in making the stone ornament fairly stable.
Things are getting worse when, instead of ensuring the stability of heavy stone ornaments, a sign can be taken as good enough instead! Particularly distressing is the additional sign regarding children! Good grief, what kind of hazardous place is this? Actually, it is a simple garden centre!