Transmission spectra of the hydrogen Balmer line profiles (Hβ, left; Hα, right) published by Yan & Henning (2018, green), Cauley et al. (2019, black), Turner et al. (2020, blue), and Wyttenbach et al. (2020, orange). The magenta line is the weighted average profile obtained considering just the profiles of Cauley et al. (2019) and Wyttenbach et al. (2020). Wavelengths are in vacuum to match those of the synthetic transmission spectra (see Sect. 4). The data have been rebinned by a factor of five for visualisation purposes. The dashed lines are Gaussian fits to the data. The horizontal dotted line at one sets the continuum level to guide the eye.