in this connection , it must be pointed out that the judicial notice taken by this court in the castelvi case ( supra , 363 ) `` ... of the fact that the value of the philippine peso has considerably gone down since the year 1959 , '' was premised not on the par value of the peso to the dollar , but on the dollarpeso exchange rates at the time of the taking of the lots and at the time of the payment thereof .