ENM. K. Čiurlionis’ inclination for a cyclic thinking was so strong that it would lead to its spontaneous outbursts even in the cases, when he did not plan in advance to write a cyclic work. The best telling examples arc his numerous spontaneous piano musical cycles lying among the composer's manuscript sketches. Such unidentified or unrecognized up to now cycles witness that their structural nature was the composer's particularly important medium, in a way assisting him in realization his characteristic aspiration for a cosmic whole. One of such unrecognized cycles in question, consisting of two sketches (VL 335, 336), reflects those creative intentions. The second sketch has been deciphered and published in this article for the first time. The analysis showed that the mentioned two sketches form a three-movement cycle, repeating the 1st movement in a reprise-type way. The cyclic character is evidenced by structural and intentional means. Taking into consideration two levels of the cyclic form (mega- and macro-), the basic components of the sonata form have been identified, namely the key and thematic alternatives, the modulation development of the themes and the balance between the expositional and recapitulation aspects.