Śatapatha Brāhmaṇa ("of a hundred paths") 1.7.3.19

1.7.3.19

tadu ha bhāllaveyaḥ | anuṣṭubhamanuvākyāṃ cakre triṣṭubhaṃ yājyāmetadubhayam parigṛhṇāmīti sarathātpapāta sa patitvā bāhumapi śaśre sa parimamṛśe yatkimakaraṃ tasmādidamāpaditi sa haitadeva mene yadviloma yajñe 'karamiti tasmānna viloma kuryātsacandasāveva syātāmubhe vaivānuṣṭubhā ubhe vā triṣṭubhau

Now here Bhâllabeya made the invitatory formula (consist of) an anushtubh verse, and the offering-formula of a trishtubh verse, thinking, 'I thus obtain (the benefits of) both.' He fell from the cart, and in falling, broke his arm. He reflected: 'This has befallen because of something or other I have done.' He then bethought himself of this: '(It has befallen) because of some violation, on my part, of the proper course of the sacrifice.' Hence one must not violate the proper course (of sacrificial performance); but let both (formulas) be verses of the same metre, either both anushtubh verses, or both trishtubh verses.