To make a homemade weigh scale cut out two 3-by-3 inch squares of cardboard and place one square on each end of the ruler. You should then place the ruler on top of the pencil and ensure the pencil is directly in the middle and finally place a coin one on tray and the item you're weighing on the other. The next step would be to achieve a specific weight by using a coin or coins equal to the amount of weight you need and then add the substance to the tray on the other side of the ruler until the scale is balanced.
in this way ur requirement is done