Salto-Youth. (2010). Lemons. Toolbox—For Training and Youth Work. https://www.salto-youth.net/tools/toolbox/tool/lemons.278/

The oldest source we can locate for this activity is:

Artman, R. (1976). The Miami intercultural communication workshop. In D.S. Hoopes (ed.) Readings in Intercultural Communication Volume 5. Regional Council for International Education.

Rich Artman modified the activity for his chapter but he does not have the original version.