Fross, so a detailed answer to your question in the article Yevgeny Kovtun, "Victory Over the Sun" - Beginning of Suprematism "
"Our Heritage", 1989. № 2
http://www.silverage.ru/stat/pobeda.htm
And another interesting article by Valery Turchin "Iconography of the Black Square by the light of Theosophy: an icon, symbol, sign."
http://www.gelos.ru/result/inkom/blacks2.html
Incidentally, he noticed a curious continuity: a triangle Kulbin - a square of Malevich.