Measurement.define(:'ft³') do |unit|
  unit.alias :ft3, :'ft^3', :'ft*ft*ft', :'cubic foot', :'cubic feet'
  unit.convert_to(:'acre ft') { |value| value / 43_560.0 }
  unit.convert_to(:yd3) { |value| value / 27.0 }
  unit.convert_to(:in3) { |value| value * 1_728.0 }