I really liked this wine bottle holder in the shop at Honister Slate Mine. It is not bolted down. It really is a balance bar obeying the principle of moments. A 75cl bottle will have a mass of 750g of wine. Let's make it up to 1kg including the glass.Centre of mass looks about 3cm from the pivot on the table top. Centre of mass of slate holder looks maybe 6cm from pivot which would give the piece of slate as 500g.
