This is our interpretation of it, as we couldn't find the information on the website!!!
We took a couple of water bottles and I cut the top third off and we turned it upside down and fitted it in the bottom two thirds of the bottle to use as a funnel.
We then taped the jagged edge at the top with some inexpensive electricians tape (I had a pack in the cupboard)
They then stuck, lots of tape all over the bottles to make them all colourful.
The eldest MiniMad, who I think can be called MaxiMad marked 1 cm lines on a wooden spoon with a permanent marker (I keep these hidden after a very traumatic pen on sofa incident)
They then stuck googly eyes and wool hair on their "weatherman" spoons (31p from Tesco)
The on-going plan is to record the days weather, temperature and water fall in a note book and then use that for some further adding exercises.