The following must appear in a public document:
(1) Acts and contracts which have for their object the creation, transmission, modification or extinguishment of real rights over immovable property; sales of real property or of an interest therein are governed by articles 1403, No. 2, and 1405;
(2) The cession, repudiation or renunciation of hereditary rights or of those of the conjugal partnership of gains;
(3) The power to administer property, or any other power which has for its object an act appearing or which should appear in a public document, or should prejudice a third person;
(4) The cession of actions or rights proceeding from an act appearing in a public document.
All other contracts where the amount involved exceeds five hundred pesos must appear in writing, even a private one. But sales of goods, chattels or things in action are governed by articles, 1403, No. 2 and 1405. (1280a)