Banker's Utilities Co. v. Farmers' Bank of Union, 258 S.W. 17, 19 (Mo. App. 1924) (stating that principal is charged with what it should have known "by the exercise of ordinary care").
William Goessling Box Co. v. Cal Hirsch & Sons Merc. Co., 251 S.W. 438, 440 (Mo. App. 1923) (same).
Magnolia Compress & Warehouse Co. v. St. Louis Cash Register Co., 210 S.W. 125, 127 (Mo. App. 1919) (same).
Berthold & Jennings Lumber Co. v. Texas Hardwood Lumber Co., 209 S.W. 591, 594 (Mo. App. 1919) (same) (general manager).
Meux v. Haller, 162 S.W. 688, 690 (Mo. App. 1913).
Law Reporting v. Elwood Grain, 115 S.W. 475, 477 (Mo. App. 1909) (citing Kingsley v. Vitt, 51 Vt. 414).
Watkins v. Edgar, 77 Mo. App. 148 (Mo. App. 1898) (collects authorities).
See generally Restatement (Third) Agency Sec. 2.05 (2006) (estoppel) ("The principal's failure to use care enables the agent, or an actor who purports to be an agent, to misrepresent the agent's authority or to masquerade as an agent.").
For a deeper discussion of knowledge, consider Daniel S. Kleinberger, Guilty Knowledge