Mastabas: symbol scales

[gary cran]

I've filled the first one with water no problem. The walkthrough is then unclear as to which one gets the petrol. I have tried all sorts of combinations, pouring it from different sides etc. but with no success. It won't allow me to pour anything into the far right scale. Can you help please?

[Donkasta]

When facing the scales from the front, the water goes in the left one, the bag of sand in the right one, and oil (from the jerry can) in the middle one. You then have to light the oil to open the door.