Richard Mann 
Manual of Singing, for the Use of Choir-Trainers and Schoolmasters [PDF ebook] 
A Method of Learning to Sing at Sight

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Never tell your pupils that singing is an easy accomplishment; commence rather with a statement of its difficulties. At the same time assure them that steady hard work will be certainly crowned with success.