In Day & Co. v. Texland Petroleum, Inc., 786 S.W.2d 667 (Tex. 1990), the granting party, Day, Inc., leased an 80-acre tract of land from a third party by general warranty deed. Id. at 668. The entire 80-acre tract was subject to the third party's one-half non-executive mineral interest. Id. The third party expressly conveyed all executive rights to Day, Inc. Id. Later, when Day, Inc. leased ten of the 80 acres to the Shoafs, Day, Inc. excepted the third party's one-half mineral interest, as well as Day, Inc.'s own one-fourth mineral interest. Id. The deed, however, did not mention the executive right previously granted to Day, Inc. by the third party. Id. The Shoafs and Day, Inc. later executed mineral leases. Id. Texland acquired the leases covering all 80 mineral acres and completed a well on the Shoafs 10-acre tract. Id. Later, Day, Inc., suspecting Texland's predecessor-in-interest did not properly pay delay rentals to maintain its lease to the non-executive one-half interest owned by the third party, attempted to exercise executive right to the interest by leasing the minerals to the president of Day, Inc. Id. The Supreme Court held the executive right in the mineral estate passed to the Shoafs under the general warranty deed even though it was previously severed from the mineral estate and conveyed to another party, but unmentioned in the general warranty deed. Day, 786 S.W.2d at 669. The Court found, although the executive right was severed from the mineral estate, "it remains an interest in property, an incident and part of the mineral estate like the other attributes such as bonus, royalty and delay rentals." Id. The Court held the previously severed, but not reserved or excepted, executive rights were conveyed under the general warranty deed. Day, 786 S.W.2d at 669-70. The Court held that executive rights not expressly reserved or excepted in a deed pass under the deed. There, Day & Co. acquired an 80-acre tract of land from a third party by warranty deed. Id. at 668. The deed reserved an undivided 1/2 mineral interest, but conveyed all of the executive rights. Id. Later, Day & Co. conveyed ten acres to the Shoafs by warranty deed. Id. The deed reserved an undivided 1/4 th mineral interest for Day & Co. and identified the previously reserved 1/2 non-executive mineral interest. Id. The deed, however, neither mentioned the executive right previously granted to Day & Co. nor reserved those rights. Id. Both Day & Co. and the Shoafs executed mineral leases. Id. Texland acquired the leases to the entire 80-acre tract and completed a well on the Shoafs' 10-acre subtract. Id. Claiming that Texland's predecessor-in-interest had not maintained its lease on the undivided 1/2 non-executive mineral interest, Day & Co. attempted to exercise the executive right to the mineral interest. Id. Day & Co. asserted that it owned the executive right to this mineral interest because the severed executive right was in the nature of a power of appointment. Id. As a result, it could only be transferred by express assignment under contract principles and not by implication under principles of real property. Id. Texland asserted that because the executive right to the undivided 1/2 non-executive mineral interest was not expressly reserved or excepted in the deed, the executive right passed by implication to the Shoafs. Id. The Texas Supreme Court held that the executive right to the undivided 1/2 non-executive mineral interest passed to the Shoafs under the warranty deed, even though the right was previously severed from the mineral estate, conveyed to another party, and unmentioned in the warranty deed. Id. at 669-70.