Author, please: Words to contract by, singular and plural

An historical quest:  Who is the true, original author of the pieces of this poetical sentence:

The singular shall where the context so admits include the plural and vice versa and the masculine shall include the feminine as shall be appropriate.

The sentence appears, with variations, in numerous contracts. Here are two examples:

International Meat Trade Association:

Words used in the singular shall, where the context so admits, include the plural, and vice-versa and words used in the masculine shall include the feminine.

Ham Farm (Dolton and Devon, UK):

Words in the is Agreement importing the singular shall, where the context so admits include the plural meaning and vice versa and words in this Agreement importing the masculine gender shall include the feminine and neuter genders and vice versa and words noting natural persons shall include corporations and vice versa.

The pieces go back at least to 1879, and likely before. Here’s an instance from 1879: