Designed in 1906 by de Spiganovicz (the founder of the club) and MacLeod.   It was intended as a Lads Club to ‘provide wholesome recreation and amusement’ and to take boys off the street.   The foundation stone was laid on April 1906 and it had opened by the end of the year, built at a cost of £1700.    An elevation of the building with its ‘free treatment of Renaissance’ design appears in the Edinburgh Evening News on 18 Jan 1906, with the proposed accommodation as follows; Ground Floor - Refreshment Room, Kitchen, Waiting Room, lavatories; First floor - Gymnasium and hall; Second Floor - top lit works and games rooms.   The building appears in de Spiganovicz's autobiography,  ‘Mystery Man again, Reminiscences of a Tramp’ (1924), and he appeared on 'This is your life' in 1960.  Further information, and an image of the building from de Spiganovicz's biography appears here;

https://threadinburgh.scot/2024/04/13/the-thread-about-the-causewayside-lads-institute-and-the-wandering-life-of-victor-de-spiganovicz-self-described-mystery-man/