Application for the writ shall be made by petition, signed and verified either by the plaintiff or by some person in his behalf, and shall specify:

First. By whom the person in whose behalf the writ is applied for is restrained of his liberty, and the place where, naming all the parties, if they are known, or describing them, if they are not known.

Second. The cause or pretense of the restraint, according to the best of the knowledge and belief of the applicant.

Third. If the restraint be alleged to be illegal, in what the illegality consists.