A future limitation, whether executory or by way of remainder, and of either real or personal property, which is not to vest until after the expiration of or will not necessarily vest within the period fixed and prescribed by law for the creation of future estates and interests, and which is not destructible by the persons for the time being entitled to the property subject to the future limitation, except with the concur- rence of the individual interested under that limitation. Lewis, Perp. 104; 52 Law Lib. 139. Any limitation tending to take the subject of it out of commerce for a longer period than a life or lives in being, and twenty-one years beyond, and, in case of a posthumous child, a few months more, allowing for the term of gestation. Rand. Perp. 48. Such a limitation of property as renders it unalienable beyond the period allowed by law. Gilb. Uses, (Sugd. Ed.) 200. And see Ouhl v. Washington Hospital, 95 U. S. 303, 24 L. Ed. 450; Duggan v. Slocum, 92 Fed. 800, 34 C. C. A. 676; Waldo v. Cummings, 45 111. 421; Franklin v. Armfield. 2 Sneed (Tenn.) 354; Stevens v. Annex Realty Co., 173 Mo. 511, 73 S. W. 505; Griffin v. Graham, 8 N. C. 130, 9 Am. Dec. 619; In re John's Will, 30 Or. 404, 47 Pac. 341, 36 L. R. A. 242.