For a valid contract of sale of immovable property to be established, the essential elements including the purchase price (pretium) and the subject matter (merx) must be clearly proven. Where a party claims ownership based on a verbal sale agreement, they must establish with credible and consistent evidence: (1) the precise terms of the agreement including the purchase price; (2) when the agreement was concluded; and (3) that the consideration was adequate and reflective of a genuine sale transaction. The absence of these fundamental elements, coupled with inconsistent testimony and failure to formalize rights over an extended period, will result in the claim being rejected. In cases turning on the credibility of competing witnesses, the court will assess the internal consistency of each party's version, corroboration through documentary evidence, and the inherent probability of the competing accounts.