Chikara Ishi (strength stone) or Chi-Ishi (short name)
You will need several two and a half litre plastic buckets (plastic paint pots are ideal)
Six inch (15cm) nails
A broom handle or doweling, one and a quarter inches (3cm) diameter
The length for each Chi-Ishi should be eighteen to twenty inches (46 to 51cm) as a rule of thumb the top of the handle should be level with the top of your knee.
A bag of ready mixed concrete with 10mm pebbles (optional)
Drill two holes in the base of the broom handle, north to south and east to west, bang the nails in the shape of an X.
Add water to the mix, make sure the consistency is not too watery.
Place the handle in the bucket then add the mix, as you add more tap the side of the bucket this will get rid of any air in the mix.
Leave for about a week, it should then be rock hard.
Carefully take a Stanley knife and cut the bucket all the way down to the side, gently pull out the Chi-Ishi.
Rub the handle with fine sand paper to clear it of all cement residue.
As to the weight, the size of the bucket and depth of concrete poured will determine that.
You can paint the concrete but not the handle as during use the handle will become sweaty
and paint or varnish will stop this being absorbed into the wood.