The following shall produce no effect:\n(1) Substitutions in trust not made in an express manner, either by giving them this name or by imposing upon the substitute the absolute obligation of delivering the property to a second heir.\n(2) Provisions containing perpetual prohibitions to alienate, and even a temporary one, not within the limits fixed in section 2308 of this title.\n(3) Those imposing upon the heir the charge of paying a certain income or pension to several persons successively beyond the second degree.\n(4) Those, the object of which is to leave to a person the whole or part of the inheritance in order that he may apply or invest it, according to secret instructions given him by the testator.\nHistory —Civil Code, 1930, § 714.
Puerto Rico Legal Code