I worked with physically challenged adults and raised their tables by cutting 4 pieces of 4"x4"x1' lumber. I then drilled a 1" shallow "hole", the size of the bottom of the table legs, in the center of each of the 12" cut sections and then sat a table leg in each "hole". If a higher table was needed a just stacked and nailed or screwed another board of whatever thickness was desired on to the 4x4. The reason for not using the top end of the 4x4 pieces was that the 12" length base provided more stability. The same method can be used to raise beds, couches and other furniture.
Some "raisers" or now being sold for the disabled and can be found where those supplys are sold.......Lydia