Was Jakob Liiv the author of the first Estonian sonnets?

According to Bernard Kangro’s Eesti soneti ajalugu („History of the Estonian sonnet”, 1938) the first Estonian sonnet ever written was Õnnesoov isamaale („Congratulation to Fatherland”) by Matthias Johann Eisen, published in 1881, which has ever since been regarded as the birth year of the Estonian sonnet.
     However, there are two Estonian sonnets dated to earlier years by their author Jakob Liiv (1859–1938). The sonnet Isale 50 aastaseks sündimise päevaks („To Father on his 50th anniversary”) bears the date 1878, and Asjata („In vain”) – 1880. Both were published later than Eisen’s poem: Isale... in 1886 (undated) and 1903 (dated), while Asjata was published even later. The problem is whether Jakob Liiv actually wrote the sonnets in those years, which would mean a three-year prolongation of the history of the Estonian sonnet. To find an answer, the two sonnets are first analysed from the aspect of the technique of verse (metre, rhyme) in the context of the period as well as Liiv’s oeuvre, after which the two are referred to the author’s biographical background. The article fails to provide a definitive answer, though.
     The biographical data seem to support Liiv’s own datings, as by 1878 the young Liiv had been practising poetry for several years, also showing the results to his teacher Johann Jürgenstein. In addition, he was already acquainted with the oeuvre of Nikolaus Lenau, whose poetry, especially the sonnets, has been pointed out by Liiv as an influential example. Questions can be raised, however, about the technique of verse. Asjata, for example, is the only amphibrach in Liiv’s early oeuvre, moreover, the rhyming technique used is also more characteristic of the mature Liiv. Possibly, the truth is somewhere in the middle: Jakob Liiv may indeed have written those sonnets as dated, but edited them thoroughly before publishing.